queryservice: Create a DUAL fake table

Now that table names are case sensitive, we need to allow
both dual and DUAL as fake tables.
queryservice: actually make dual work
queryservice: add TODO to fix dual correctly
bsongen: non-struct simple types
Store a history of health.Run results.
Allow history.History to deduplicate records.
health.Record: define methods for display and deduplication.
Fix typo in health.Record.Class.
health.Record.Class: really fix it, write test.
Fix silly bug in health module.
WIP connection and cursor class for vtgate v2.
Added additional methods and cleaned up some code.
Small fixes.
more cleanup.
Added function to convert shard_name to keyrange.