Move classes from *.mapping.sql to *.mapping.base.sql
The implementation for SqlParser is simplified by adding one more method
interface that requires IDatabaseMetadata. This action removes the
unnecessary abstract class (i.e., SqlMappingParser).
Move classes from package *.mapping.base.sql.parser to
*.database.sql.parser
Remove the unnecessary classes from the SQL parser API.
Update the mapping parser framework.
Rename class.
Remove the checking MutableMappingSet in the parser implementation. But
instead move it to the handler.
Import tidy.