Fix OpenGL errors.

Fixes MovingBlocks/Terasology#461.

The switch statement requires GLSL 1.3, and OS X doesn't support it, so
fake it with if-then-else statements.

The graphics card in my Macbook Pro doesn't support FBOType.NO_COLOR
either, and I suspect this applies to multiple Mac models.

Tested on a MacBookPro5,3, with OS X 10.8.2.
Fixed a bug in the railgun tool. TunnelAction now cancels the activate event if it end up destroying no blocks. I also increased its priority to HIGH so that PlaySoundAction is lower than it. The result is that an explosion sound will only play if the railgun actually destroys blocks
Pressing right arrow key in chat while in debug mode no longer fast-forwards time
Merge #468 from @sdab - railgun tweaks
Update credits and some misc
Merge pull request #462 from philip-wernersbach/better-osx-support

Fix OpenGL Errors
Adaptation of the versionInfo to the TerasologyLauncher code
Little changes to checkstyle.xml (copied from TerasologyLauncher)
Merge #474 from @mkalb - checkstyle tweaks
Add a couple more contributors to the credits