Experimental features; proofreading; URL pagination (BBQ)

* Experimental features (with fallbacks if VexFlow is 'standard')
  * breve
  * tenor clef (transposing)

* Proofreading
  * added breves
  * removed unnecessary ties
  * corrected wrong octaves against printed edition (esp. on staff 2)

* URL pagination
  * using jQuery BBQ to get/push state from URL fragment
  * each page now has its own URL fragment