Presto: Allow setting location property for managed tables too

[shubhamtagra]

Currently, CREATE TABLE creates an external table if we provide external_location property in the query and creates managed table otherwise.
But Hive allows creating managed tables with location provided in the DDL so we should allow this via Presto too.

This will also change SHOW CREATE TABLE behaviour to now show location even for managed tables.

We can do this:

1. Have a boolean property "external" to signify external tables
2. Rename "external_location" property to just "location" and allow it to be used in both case of external=true and external=false

c.c. @electrum I see your commits around this. Let me know if you have other ideas around this.

[electrum]

This sounds good to me. We probably want to accept the old property on creation for a while, to keep compatibility with existing DDL.