Lots of small improvements to the melodies exercise:

[u]Melodies:[/u]

* The degrees are now selected individually, no longer using scales. Similarly to how it is like in the degrees exercise. 

* Added the full names for each degree under the hexagons.

* Fixed score display for ES language.

* Added a hear drone option like the one present in the degrees exercise.

* You now can't get the same degree twice in a row.

* Fixed spacebar not reseting the exercise progress.

[u]Other changes:[/u]

* Added example degrees on the fretboard like the ones in the interval exercise.

* Made the degrees and interval full text bigger so it's easier to read.

* Added ES language degree names.

* Re-ordered the exercises so that degrees come on by default as it's going to be the main focus of the application along with melodies from now on.

* Fix for some interval examples not showing up when the max fret size was set to a low number.

* Fix hold button for drone not working when interacting with it using the mouse.

* Lowered drone note volume.