Refactor classes in soc/logic/models to make more use of inheritance. Add some missing classes, such as soc.logic.models.group.Logic, so that key name similarities between various Groups can be exploited via inheritance instead of repetition of code. Patch by: Todd Larsen

Replace HomeSettings with Presence Model class. Replace SiteSettings with Site Model class. Derive Group Model class from Presence, adding the "home page settings" properties in a Melange site presence to every Group. Patch by: Todd Larsen