Codebase specification is too hard for large projects

[Pennycook]

Accurately describing all the files in a codebase using regular expressions is very difficult for large projects.

Code Base Investigator already supports loading commands from compilation databases, but the user must still specify which files appearing in the compilation database should be considered part of the codebase.

There should be a mode that allows Code Base Investigator to discover the files in a codebase from the platform definitions.