Changed 'i' duration to 'e'. Gave up on case-insensitive pitch classes to clean this up.
Standardized interval names and removed intervals from grammar that did not correspond to the Lang::Intervals constants
Defined pseudo-constants for augmented and diminished intervals in Lang::Intervals and the MTK grammar.
Also made various improvements to the docs (e.g. more interlinking between Core and Lang classes)
More improvements to the documentaiton in the Lang module
All Lang::Pitches constants are now documented