Mark toggling and create missing and non-save properties for brush selection

Re-using this properties were rather confusing -- selecting mask brush once
lead to changes in behavior of other brushes hotkeys.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56957 954f8c5b-7b00-dc11-b283-0030488c597c