Updated data submodule

I did a bit of cleaning up the history from old music files
Updated submodule
Added oggenc to Travis config
Updated INSTALL.md to reflect latest changes to music repository
 #335, #348, #352

I don't know what I'm doing anymore :/
I should set up dev envrioment on Windows so I don't have to commit every time I want somebody on Windows to test if my changes work
Updated data submodule
COLOBOT: Gold Edition -> Colobot: Gold Edition
Fixed icon on Windows; updated properties in .rc file
Merge branch 'dev'

Conflicts:
	data
Release alpha-0.1.4
Post-release alpha-0.1.4