Revise IndexedPiece and TemplateIndexer to Allow Score as Input

There will be some cases where we want an entire stream.Score, not just
its Part objects.

(cherry picked from commit 4499d1d41839df5973361b702ec64a8195281107)
Add Tests for LilyPondIndexer.__init__()
Add Tests and Corrections for LilyPondIndexer.run()
Quieted pylint a bit, for things it shouldn't worry about
Include More Mocks for 'lilypond' Module Tests

Thought I was just being paranoid, but I actually caught an error in the
program logic...
Renamed template_test.py to test_template.py

It made zsh autocompletiong a little less helpful. NO MORE!