[ABRS-24] Database reader service
[ABRS-24] Created MySQL-specific ConnectionParams
[ABRS-24] collecting database info
[ABRS-26] added some operators
[ABRS-24] Some refactoring
* Moved DbReaderService and its related classes to pl.edu.agh.two.abrs.service.db
* Created testConnection() method in DbReaderService
* Added javadocs in DbReaderService
Merge branch 'ABRS-24-db-reader'
Merge branch 'master' into ABRS-25
[ABRS-25] Made DbReaderService.getColumns() to return List<LocalSchemaColumn>