mono processing and optional, separated file parameter outputs

[tomika]

Hi,

First of all thanks for sharing your work. Secondly I wanted to create mono output for mono input file, but (since this is the first time I use python) I could not manage to avoid completely the double processing of both channels, so only input FT processing is simplified. IMHO that would be way better if the whole separation would not be performed twice (or on twice amount of data), but this is the best I could do for at least now. Also I've added parameters to create optionally voice and instruments files (since I don't need instruments, but others may only want those).