Proper names of notes

The name of displayed notes when played on the keyboard is **always the same**, whereas they should depend on the context of the chord. For instance, in a Ebmin7 chord, the 3rd should be "Gb", and not "F#".

Same goes for the chords themselves. We will never be displayed a C#maj7 chord for instance, because "C#" does not exist in the set of available root notes. Only "Db" is hardcoded in the `midiPitchToNoteName` object. Being asked for both would add a bit more variety to the game and would be closer to a real-life situation, i.e facing a lead sheet.