(pj64tosrm) Improve arg handling and add export support

- Supports drag'n drop of save files over the executable.
- Added proper mempack formatation.
- Improved Windows support.
- Added overwrite confirmation dialogs/prompt.
- Support for libretro-mupen64+ latest srm format.
Merge pull request #120 from heuripedes/master

(pj64tosrm) Improve arg handling and add export support