improved KERN processing for KERN Opus -- added Palestrina Corpus (Bret Aarden)

git-svn-id: http://music21.googlecode.com/svn/trunk@3364 5c16147e-a200-11de-b0cc-ab0ad15e60d0
Fixed docs

git-svn-id: http://music21.googlecode.com/svn/trunk@3365 5c16147e-a200-11de-b0cc-ab0ad15e60d0