Fix for CRM-21180: Inline changes to custom fields aren't reflected in custom greetings.

Fix for CRM-21180: Inline changes to custom fields aren't reflected in custom greetings.

Includes unit test.

Toward CRM-21180: Better static var handling.

Toward CRM-21180: removed static vars; removed unused method parameters.

CRM-21180 add unit test for custom field being set in address

CRM-21180 Inline changes to custom fields aren't reflected in custom greetings

This incorporates Allan's work to cause custom fields to be updated
when a custom value is updated. These have been reconciled with the changes to allow
greeting fields to be set to null per CRM-21474

m