Simple Contacts: Add support for relations

[rlieger]

A ContactRelation can be used to express a relation to another person (e.g. spouse, friend, colleague) within a contact. This concept is supported by both Android (ContactContract.Relation) and vCard 4.0 (RELATED) and should thus also be supported in SimpleContacts. Note: Like most fields, displaying relations for a contact is optional and can be enabled/disabled in the manage-visable-fields dialog. It is disabled by default, so to see my code in action be sure to enable it...

I have added suitable code for both the base types (in Simple-Commons) and the application logic for the viewing/editing the databases (in Simple-Contacts). Thus to obtain a working system, pulling both Simple-Commons and Simple-Contacts is necessary!