Simpler "drop scramble"

[pyongjoo]

I noticed that its syntax includes the original table; however, since the scramble itself is a unique identifier, I don't we need the original table name.

I think it is good to have an extra checking, but just in case the user simply issues "drop scramble some_schema.scramble_table", we can drop the table.

[pyongjoo]

Can you also make scrambling queries use the default schema if available?

I just noticed that if the schema name is not explicitly specified (after a 'use' query), a syntax error is thrown.