Bread 2.0 released

I think we can all agree this loaf doesn't deserve an update. But it got one anyway.

All platforms:

• You can now listen to your own music in-game by placing a file called "custom-music" in the game folder. Must be MP3 (.mp3), Ogg Vorbis (.ogg) or PCM WAV (.wav).
• Flour bags are now partially semi-transparent to make the intended collision points more obvious.
• Removed some unnecessary physics calculations. This might have a minute improvement on performance if you're CPU-bound.

Linux:

• Stop focusing the window all the time. This brings its behaviour in line with the Windows version and enables you to interact with other applications while the game is running using the keyboard.
• Removed JRE manual pages from the release. This fixes a symlink error upon extraction.