In jdbcUrl add config to create External + purge table by default

External + purge tables are more backward compatible with the old managed tables.

Applications can use a HS2 URL that sets the session level property for default table type to external-purge tables to be true.
As part of this we need a notion of a "session level only" config parameter(s).

Adding a new jdbc config: hiveCreateAsExternalLegacy, a hs2 config hive.create.as.external.legacy, when set to true, create external purge table by default.

Adding MANAGED keyword. "create managed table" will create table based on hive.create.as.acid and hive.craete.as.insert.only values, not impacted by the new config.