Added an option for normalize_all that keeps the active group at its existing weight while normaling all other groups around it.
Thsi makes it easy to paint up to 100% where all other groups will use progressivly less until the active group is 100% and all others are 0.
Added weight operators to the toolbar
* Fix AAO showing Distance property even though it is not supported.
* Fix texture buttons not displaying texture stack from the node material.
* Small visual tweak to particle mode options.
