few changes for PyPi
quarterLength selectively produces Fractions
optional Fractions almost everywhere
all offsets etc. are rational or power of 2 floats

Speed reduction is less than 1%.  Made up in test suite by optimizing
abc/translate.
OrderedDict for CHORD_TYPES
Merge branch 'version2'

Conflicts:
	music21/base.py
	music21/corpus/metadataCache/core.json
	music21/duration.py
	music21/note.py
	music21/sites.py
	music21/stream/__init__.py
metadataCache/cor.json fix