Parser track

Realized we already had track functionality - just because we added the '.' (ie serial) functionality earlier.
This will really become solid when we have the semcheck make sure that '.' is only being used to combine chords. 

Also- added rest functionality only for literals; adding funtionality for IDs should also be easy- we need to do this for chords and notes as well. I will take this on tomorrow and make our *_CR for note, rest, chord be able to be initialized with literals or ids.