Handle Mapping of Query Conditions for Grouper Plugin

Handle mapping of query conditions (primarily for READ, but potentially for UPDATE) from cake's SQL like notation to grouper calls in a more generic/elegant fashion (CoGroup[Member]Source.php in plugin).

It might make sense to force all CoGroup/CoGroupMember operations to go through model specific methods rather than using find() (eg: CoGroup->retrieveById(27)) which constrains what conditions are used according to what the plugin currently implements