[cwconfig] Add optional configuration param to load a UI cube before other cubes
Needed later on to load UI cubes such as legacyui, and one day squareui.
option_group_changed('port', 'main', 'web')
option_group_changed('query-log-file', 'main', 'web')
option_group_changed('profile', 'main', 'web')
option_group_changed('max-post-length', 'main', 'web')