[invader] inconsistent path separator behavior throughout various tools.

[Aerocatia]

When running on Linux, various invader tools will fail if you give them a tag path that uses windows path separators.
This is not too unreasonable since the game natively uses these internally.

Ideally invader should abstract this away from the user and support both types of paths separators for tag paths and convert them to the correct format as needed.

[Aerocatia]

Also related is issue #129