Fix behavior for USE catalog/schema

Fix https://github.com/facebook/presto/issues/1925
Add use catalog.schema
Not deprecate USE CATALOG <catalog> yet
Add two constructors: one that takes a catalog and schema and one that takes just a schema. Keep separate fields for each (make the catalog `Optional`). Make `getCatalog` return `Optional<String>`. Also, update the grammar rules to match schema vs catalog+schema separately and call the right constructor.