1.1 documentation update

Added description of axis locking
Added Grid Snap shortcut and expanded it's description (+ warning
against it's use)
Updated brush rotation shortcuts to be alt instead of ctrl
Deleting objects is now correctly stated as Backspace key
duplication documentation update

Added description of new duplicate and move commands.
Duplicate description now says it duplicates in place
clip tool documentation update

Updated shortcuts
Documented split brush entities remaining in entity
Documented clip tool remembering last clip mode
Added preferences window information.
Merge branch 'master' of https://github.com/necros0/TrenchBroom
Minor documentation changes.

Signed-off-by: Kristian Duske <kristian.duske@gmail.com>
Merge branch 'master' of https://github.com/Scampie/TrenchBroom