UI Changes Drop 2:
-Switch to using a grid view to display the chords/measures (which I am
currently calling "song blocks")
-Clean up layouts to accommodate this grid view better (for example,
move or remove scroll views so I don't have a grid view inside of a
scroll view).

Implement basic part switching (right now it is hard coded with Verse,
Chorus, and Verse + Chorus). Need to generalize this for when I refactor
songs.