add vtctl support to alter vschema using sql statements
add vtctl support to alter vschema using sql statements

Add new flags to ApplyVschema to be able to take a sql ddl statement
either on the command line or in a file to enable vschema changes
without having to edit the whole json file.

Signed-off-by: Michael Demmer <4b836671cce77b1b2fbe63e5b2a1661879d8af44@slack-corp.com>

enisoc/vitess,vitessio/vitess,HubSpot/vitess,davygeek/vitess,HubSpot/vitess,tinyspeck/vitess,davygeek/vitess,dcadevil/vitess,enisoc/vitess,mahak/vitess,HubSpot/vitess,dcadevil/vitess,dcadevil/vitess,tinyspeck/vitess,vitessio/vitess,enisoc/vitess,vitessio/vitess,vitessio/vitess,davygeek/vitess,HubSpot/vitess,tinyspeck/vitess,dcadevil/vitess,HubSpot/vitess,HubSpot/vitess,enisoc/vitess,tinyspeck/vitess,mahak/vitess,davygeek/vitess,mahak/vitess,mahak/vitess,tinyspeck/vitess,davygeek/vitess,enisoc/vitess,vitessio/vitess,HubSpot/vitess,davygeek/vitess,dcadevil/vitess,vitessio/vitess,vitessio/vitess,dcadevil/vitess,HubSpot/vitess,enisoc/vitess,tinyspeck/vitess,davygeek/vitess,mahak/vitess,mahak/vitess,tinyspeck/vitess,enisoc/vitess,vitessio/vitess,mahak/vitess,dcadevil/vitess,mahak/vitess