Create / Drop Schema support

[smoothdeveloper]

@rspeele would you mind giving a look at smoothdeveloper#1

I've implemented basic stuff to get create schema and drop schema parsing and translation.

I'm wondering if there is support in the library to explicitly avoid such feature with specific backends? SQLite won't support the generated statements.

[rspeele]

Regarding avoiding specific backends, normally this is handled by failing during the backend translation stage. Like SQLite ALTER TABLE