fix ScreenGameplaySyncMachine crash

was not setting steps to null, caused access violations
Merge pull request #255 from sigatrev/SyncMachine

fix ScreenGameplaySyncMachine crash
dear github: our travis build is broken in a pretty serious way (The command "sudo apt-get install libc6-dev" failed and exited with 100), and I know this isn't travis-support nor the right place for it but I thought I should let someone outside of IRC know the reason for it thanks
Added NoteSkinManager::GetDefaultNoteSkinName so that PlayerOptions can avoid clearing the noteskin when the clearall mod is used.
Merge pull request #256 from kyzentun/NoteskinClearFix

Fix crash when "clearall" is used.
Didn't realize RollingNumbers was supposed to have negative velocity.
add TextEntrySettings documentation to ScreenTextEntry
Added One_Screen_Example_Theme as a minimal example.
Report error on fetching empty string metric instead of crashing.
Merge branch 'master' of github.com:stepmania/stepmania