Created spec file for SQL::Builder class. Created the set of unit tests for save_sql methods.
Fix some validators specs to prevent generate SQL script files during tests.
Now DataColumnSchema instance contains the reference to owner table instead of just table name.
Passed table schema instance instead of just table name to SQL::Builder class during SQL generation.
Implemented functionality creating the separate folder for database during SQL scripts generation.
Made SQL::Builder implementation more clean and DRY.
Implemented SQL script generation in SQL::Builder class.