A few enhancements to contactField handling:
* Caching readFields() responses because this data should not be volatile
* Added support for returning the fields for contacts (returns all by default)
Verifying that all submitted contactField data comes back and matches
Added another test to make sure invalid contacts error
Added the ability to update contacts
* Added update_contact[s]() methods
* Moved the building of contactField data out into _construct_contact_fields()
Added a test for updating contact data
Finish field-manipulation