This addresses some deprecation warnings in both our datagrid code and

in Django Evolution.
The load_extra_state() methods in datagrids now return lists of

modified fields, instead of booleans. This is used for more selective

profile saving, and was introduced in Djblets 3.
Django Evolution 2.2 introduced a new top-level DJANGO_EVOLUTION

setting, which nests other settings. We now use this instead of a

top-level CUSTOM_EVOLUTIONS setting.

Verified these deprecation warnings went away.
Tested that the settings saved in the datagrids used in

load_extra_state() ("Show Closed" and "Show Archived") were both

properly preserved and loaded.