Fix extracting dols.

There is no "/" after partition number when extracting a dol. Also the .remove is completely unneeded.
Merge pull request #169 from RachelBryk/extract-dol

Fix extracting dols.
Clean up FileHandlerARC.cpp/.h

- Removed parentheses from the returns.
- Put the function declaration headers back on a single line.
- Make FindFileInfo's parameter a const string reference.
Simplify file tree building for the filesystem view.

Technically this also simplifies on disc filename building in general.