add a patch method to update the message_last_read field in _user_set…

[yang-ruoxi]

• Added patch_user_time_settings() in _user_settings route, which takes just a consumer_id and the datetime object that was passed as an isoformat string (which will later be translated back into the datetime object at the server side )

• Added _patch_resource in the BaseRester to accommodate this change

[munrojm]

This looks good. Happy to merge once we release maggma and emmet.