Python cleanup.

Small refactoring and standard cleanup:

- No more from...import* lines (so static analysis works)
- Removed unused variables/imports
- Use python builtins where possible, and use python's names (no renamed fnmatch).
- Cleaned up some of the algorithms and made them more pythonic (broke out functions, keep to the left, use return statements instead of break-chains).
- Add an argument parser to wad2obj.