add what a field was changed from (and not just to) in the comments and activity section

Currently when a contact uses a magic link their updates are pushed into the comments and activity stream saying something like, "name changed to Fred," but it would be helpful to know what it was changed from in some cases to understand the history of a record.

e.g. "Name change from William to Fred"
e.g. "Zip changed from blank to 73938"
etc.