Python: Copy Python extractor to codeql repo

python/extractor/python_imports.py

@@ -0,0 +1,10 @@
+#!/usr/bin/env python
+'''This module sets up sys.path from the environment
+and runs the .import file generation.'''
+
+import python_tracer
+
+if __name__ == "__main__":
+    python_tracer.load_library()
+    import semmle.imports
+    semmle.imports.main()