Supports only a minimal subset of the project layout specification;
enough to work with the transformers produced by the CLI when building
an overlay database.
This generalizes the location cache to allow multiple sources to be
extracted in the same trap file, by adding `file_label` to `Location`,
and therefore to location cache keys. This will be used by the Rust
extractor.
Since locations for any given source file are never referenced in any
TRAP files besides the one for that particular source file, it's not
necessary to use global IDs. Using fresh IDs will reduce the size of the
ID pool (both on disk and in memory) and the speed of multi-threaded
TRAP import.
The one exception is the empty location, which still uses a global ID.
Replace the `file_extensions` field with `file_globs`, which supports
UNIX style glob patterns powered by the `globset` crate.
This allows files with no extension (e.g. Dockerfiles) to be extracted,
by specifying a glob such as `*Dockerfile`.
One surprising aspect of this change is that the globs match against the
whole path, rather than just the file name.
This is a breaking change.
