Added

• Pass overwrite flag to dithor, the flag was ignored for this algorithm
• Pass overwrite flag to Glitch algorithms (duplicate, replace, variable filter, wrong filter), the flag was ignored for those algorithms
• Support for transparency in Glitch algorithms, with this change all glitch and effect are creating transparent png when the input has some transparency. 

Changed

• When the output filename already exists and the overwriting is deactivated the newly created filename has now a timestamp in it's name.