refactors migration table services to basic implementation
taken out of the Mysql and Sqlite plugins
deletes MySqlMigrator helpers (no longer needed)
implements correct commands for MySQL and BaseSql
correts arg for QString (removes duplicate call)
uses config.h instead of no longer existing BaseSqlMigrator.h
removes no longer used SqliteColumnService.h
removes no longer existing include to BaseSqlMigrator.h
adds constructor for empy Structure::Column
removes BaseSql-Files which no longer exist from src.pro
ignores known warnings in tests
drops database to begin of test (cleanup sometimes doesn't work?)
adds PostgreSQL plugin and tests