Merge branch 'master' into replication
bsongen: Add pipe through goimports
AllowPassDML -> StrictMode

Change allow-pass-dml flag to strict-mode (the opposite).
Additionally strict-mode also enforces the STRICT_TRANS_TABLES
setting.
queryservice: improved strict mode check
fix strict mode command line arg
VTGate V2 implementation and sandbox test improvement
Merge branch 'bson'
bsongen: handle nesting with unique var names
bsongen: prefix local vars with _
bsongen: more tweaks
bsongen: better bson.Null handling
bson: encode maps & slices as empty if nil.

I was encoding them as bson.Null, but existing
clients expect empty objects instead. Legacy wins.
bson: change custom encoders to not use Null for slices and maps
bson: RecordLen -> Close
bson: improved nil value handling for custom marshalers
Implemented re-resolve on error for topology and added tests.
removed superfluous line from test.
Cleanup for readability and corresponding changes to tests.
Minor cleanup for readability.
First pass at vttablet health check.

Moving a lot of stuff around too.