Alpha 4 source release, major changes include:

- changed icon to Paragon
- modified/upgraded/ported OSX XCode project  and Linux build settings to Paragon and pioneer's recent changes (SDL2 etc)
- Added reset keybindings button
- Paragon GUI theme changes
- Fixed a lot of bugs
Merge pull request #333 from MeteoricGames/alpha4_rc

Alpha 4 source release