Feature/fix schema specified

Fix for two problems associated with schema_specified feature:

First:
If you pass 'schemas' parameter in DB constructor, function refresh_schema never use schema_specified query.
Reason: 
First if in refresh_schema is always False (because of 'schema_specified' in self._query_templates is always False)

Second:
If you use this schema_specified_query for MySQL you will get:
TypeError: not all arguments converted during string formatting  (because of  {table} in query}