R1:ddce177d8157

Add a name token table so on-demand typeaheads can match last names

Summary: See T585. We currently don't match middle/last/nth names in on-demand
tokenizers. Build a table so we can match them.

Test Plan:
Ran upgrade script, verified table looks sensible. Searched for "priestley" in a
tokenizer, got a bunch of test account hits.

mysql> select * from user_nametoken;
+-------------------+--------+
| token | userID |
+-------------------+--------+
| evan | 1 |
|…