CORE-1826 Unique constraints not captured in MSSQL
changeLogSync listener configurable on Liquibase object
CORE-1825 Snapshot does not capture foreign keys referencing unique constraints

Mysql in particular throws a null pointer exception with a null value passed to getCrossReferences foreign schema/catalog. Reverted to getImportedKeys().

Also updated integration tests to use new SDK vagrant boxes
Merge branch 'master' into LB-3.1-testing