Merge pull request #1005 from diizy/stable-1.1

Add "clear track" option, fix copying of tracks from song ed -> bb ed
Monstro: add newlines to helptexts
Merge pull request #1016 from diizy/gfx

Monstro: add newlines to helptexts
Fix bbtrack undo/redo bug
Fix #790
Merge pull request #1019 from diizy/gfx

Fix bbtrack undo/redo bug
Change redo shortcut from ctrl-r to ctrl-y
Ctrl-y is more standard and used in many applications, ctrl-r is used pretty much nowhere.