Fixed crash in creating user screen, which occured after rename player.

It's a bit quick and lazy fix. Probably other variables should be cleared too.
Remove unecessary files.
Fix memory leak found by vlj
Fix build
Fixed some layout problems in some screens
Fix music stop problem when loading track selection screen

Populate irrlicht's texture cache on startup with all the track
screenshots to avoid the problem
Fix translation problems in random GP screen
Changed button text in GP name input dialog
Merge remote-tracking branch 'upstream/master'