sarif-extract-multi: extract combined tables from multiple sarif files

This command introduces a new tree structure that pulls in a collection
of sarif files.  In yaml format, an example is

    - creation_date: '2021-12-09'   # Repository creation date
      primary_language: javascript  # By lines of code
      project_name: treeio/treeio   # Repo name-short name
      query_commit_id: fa9571646c   # Commit id for custom (non-library) queries
      sarif_content: {}             # The sarif content will be attached here
      sarif_file_name: 2021-12-09/results.sarif # Path to sarif file
      scan_start_date: '2021-12-09'             # Beginning date/time of scan
      scan_stop_date:  '2021-12-10'             # End date/time of scan
      tool_name: codeql
      tool_version: v1.27

    - creation_date: '2022-02-25'
      primary_language: javascript
      ...

At run time,

    cd ~/local/sarif-cli/data/treeio
    sarif-extract-multi multi-sarif-01.json test-multi-table

will load the specified sarif files and put them in place of
`sarif_content`, then build tables against the new signature found in
sarif_cli/signature_multi.py, and merge those into 6 larger tables.  The
exported tables are

    artifacts.csv  path-problem.csv  project.csv
    codeflows.csv  problem.csv       related-locations.csv

and they have join keys for further operations.

The new typegraph is rendered in

    notes/typegraph-multi.pdf

using the instructions in

    sarif_cli/signature_multi.py

sarif_cli/typegraph.py

@@ -11,124 +11,6 @@ from dataclasses import dataclass
 from typing import *
 import pandas as pd
 
-# 
-# Structure graph from ../../bin/sarif-to-dot -u -t -f results.sarif
-# 
-struct_graph_2022_02_01 = (
-[   ('String', 'string'),
-    ('Int', 'int'),
-    ('Bool', 'bool'),
-    (   'Struct2685',
-        (   'struct',
-            ('index', 'Int'),
-            ('uri', 'String'),
-            ('uriBaseId', 'String'))),
-    ('Struct5277', ('struct', ('location', 'Struct2685'))),
-    ('Array4640', ('array', (0, 'Struct5277'))),
-    ('Array7069', ('array', (0, 'String'))),
-    (   'Struct9543',
-        (   'struct',
-            ('semmle.formatSpecifier', 'String'),
-            ('semmle.sourceLanguage', 'String'))),
-    ('Struct2774', ('struct', ('text', 'String'))),
-    (   'Struct6299',
-        (   'struct',
-            ('endColumn', 'Int'),
-            ('endLine', 'Int'),
-            ('startColumn', 'Int'),
-            ('startLine', 'Int'))),
-    (   'Struct4963',
-        (   'struct',
-            ('artifactLocation', 'Struct2685'),
-            ('region', 'Struct6299'))),
-    (   'Struct2683',
-        (   'struct',
-            ('id', 'Int'),
-            ('message', 'Struct2774'),
-            ('physicalLocation', 'Struct4963'))),
-    ('Array0350', ('array', (0, 'Struct2683'))),
-    (   'Struct4199',
-        (   'struct',
-            ('primaryLocationLineHash', 'String'),
-            ('primaryLocationStartColumnFingerprint', 'String'))),
-    ('Struct3942', ('struct', ('id', 'String'), ('index', 'Int'))),
-    (   'Struct4055',
-        (   'struct',
-            ('locations', 'Array0350'),
-            ('message', 'Struct2774'),
-            ('partialFingerprints', 'Struct4199'),
-            ('relatedLocations', 'Array0350'),
-            ('rule', 'Struct3942'),
-            ('ruleId', 'String'),
-            ('ruleIndex', 'Int'))),
-    ('Struct0987', ('struct', ('location', 'Struct2683'))),
-    ('Array1075', ('array', (0, 'Struct0987'))),
-    ('Struct4194', ('struct', ('locations', 'Array1075'))),
-    ('Array1597', ('array', (0, 'Struct4194'))),
-    ('Struct7122', ('struct', ('threadFlows', 'Array1597'))),
-    ('Array9799', ('array', (0, 'Struct7122'))),
-    (   'Struct9699',
-        (   'struct',
-            ('codeFlows', 'Array9799'),
-            ('locations', 'Array0350'),
-            ('message', 'Struct2774'),
-            ('partialFingerprints', 'Struct4199'),
-            ('relatedLocations', 'Array0350'),
-            ('rule', 'Struct3942'),
-            ('ruleId', 'String'),
-            ('ruleIndex', 'Int'))),
-    ('Array6343', ('array', (1, 'Struct9699'), (0, 'Struct4055'))), # MANUALLY SORTED
-    ('Struct8581', ('struct', ('enabled', 'Bool'), ('level', 'String'))),
-    (   'Struct7849',
-        (   'struct',
-            ('kind', 'String'),
-            ('precision', 'String'),
-            ('security-severity', 'String'),
-            ('severity', 'String'),
-            ('sub-severity', 'String'),
-            ('tags', 'Array7069'))),
-    (   'Struct6818',
-        (   'struct',
-            ('defaultConfiguration', 'Struct8581'),
-            ('fullDescription', 'Struct2774'),
-            ('id', 'String'),
-            ('name', 'String'),
-            ('properties', 'Struct7849'),
-            ('shortDescription', 'Struct2774'))),
-    ('Array8754', ('array', (0, 'Struct6818'))),
-    (   'Struct7820',
-        (   'struct',
-            ('name', 'String'),
-            ('organization', 'String'),
-            ('rules', 'Array8754'),
-            ('version', 'String'))),
-    ('Struct8972', ('struct', ('driver', 'Struct7820'))),
-    (   'Struct3081',
-        ('struct', ('repositoryUri', 'String'), ('revisionId', 'String'))),
-    ('Array5511', ('array', (0, 'Struct3081'))),
-    (   'Struct3388',
-        (   'struct',
-            ('artifacts', 'Array4640'),
-            ('columnKind', 'String'),
-            ('newlineSequences', 'Array7069'),
-            ('properties', 'Struct9543'),
-            ('results', 'Array6343'),
-            ('tool', 'Struct8972'),
-            ('versionControlProvenance', 'Array5511'))),
-    ('Array0177', ('array', (0, 'Struct3388'))),
-    (   'Struct6787',
-        (   'struct',
-            ('$schema', 'String'),
-            ('runs', 'Array0177'),
-            ('version', 'String')))]
-)
-
-# 
-# The starting node is the typedef with '$schema' in the struct, also the leftmost
-# node in ../notes/sarif-structure-from-sarif-to-dot.pdf
-# 
-start_node_2022_02_01 = 'Struct6787' 
-
 #
 # Utility classes
 #