Add the possibility to delete and rename a module

[spazione]

I think the good general idea at the base is that with this tool you don't must never again touch the manifest file for every cases if is possible.

[kandebonfim]

A dirty solution to this is manually deleting/renaming the file and running itcss update to update the import file.

Anyway, I'll work on this feature for sure! Please leave this issue opened so I can remind myself of doing it.