Fixes NB#131102, fixes some memory leaks in dimming rules & dimming rules groups
Fixes NB#131102, fixes some memory leaks in dimming rules & dimming rules groups

Needs commits starting in 80511f2

Dimming rules group holds always an unique weak reference to the window dimming rules belong to

community-ssu/modest,community-ssu/modest,community-ssu/modest,community-ssu/modest