Scale based melody revamp!

A major update to the scale based melody generation! When you choose scale based melodies, you can now choose which melody structure to use. There is also a new checkbox for melody mutation that will take your scale based melody and mutate it slightly between each phrase (respecting note jumps) for subtle changes in the melody as time progresses. Please see the manual for more information! A bug where merging key parts resultet in super long songs has also been fixed. As always, remember to uninstall the old version before installing the new one!