Improve change log behavior

Our current implementation is not great and we should fix this to make things easier in the future for things like full text search etc

record direct and indirect changes to civicrm_contact. Would be good to know what tables were changed that indirectly changed the main contact table (i.e. email or address and its id)

batch all changes so that only one change record is written per contact. thus if a contact has email, address and phone changed at the same time in the same operation, it comes across as one change. (this makes it harder to record what changed)

We need this to efficiently implement full text search