UC-138 Update the user_fbconnect table and code that accesses it

Changes to record all the data necessary to disambiguate Facebook users now that we don't get a universally unique ID.

https://wikia-inc.atlassian.net/browse/UC-138
Note that this method used to return ```boolean```.  I think its more useful for it to return the mapping it just created.  The existence of the mapping is success and its absence is failure.