ADDED methods to DELETE row from TransformationFIleTasks table
minor change in operation order to be ready for FK.

MODIFIED field definition for TaskID in TransformationFiles table (from
VARCHAR to INT, in order to be ready for FK definition: TaskID in
TransformationTasks and TransformationFileTasks is INT)
minor fix on cleanTransformation method (order of execution of deletes
methods)
Merge pull request #1493 from ltomassetti/delTFT

ADDED methods to DELETE rows from TransformationFIleTasks table