Merge branch 'develop' of https://github.com/openwebwork/webwork2 into feature/new-ui-tools
some backbone documentation
changes to ignore applets and library-tree json files.
some stray backbone documentation file.
Merge branch 'feature/new-ui-tools' into develop

# By Peter Staab (70) and others
# Via Michael Gage (21) and others
* feature/new-ui-tools: (154 commits)
  fixed bugs related to the deleting and undo deleting of problems in a set.
  updated backbone to version 1.1 and some general changes the was problem sets are defined.
  Continue pulling messages out of the js files and initial switch to backbone 3
  Fixed a general error in that both the date and time wasn't being set correctly.
  Implemented Greg Kraus' suggestions regarding aria landmarks
  Fixed Issue #190.
  Added a paginator to all problem list views to address issue #203
  Fixed textbook section display in Library Browser.
  bug fixes and new features for the Textbooks part of the Library Browser.
  Bug fixes to the library tree and library browser.
  The Import problem sets is now complete and some minor ui changes.
  Beginning of Import/Export of sets.
  The calendar now has a different model underneath and has increased performance.
  Fixed Issue #191
  Fixed Issue #198
  Added and changed many places to send notifications to the user.
  Added answer_date to the calendar.
  Fixed issue #202.
  Got rid of old variables that are no longer used.
  Added a textbook view to the Library Browser and many little bug fixes throughout the Homework Manager.
  ...

Conflicts:
	.gitignore
Merge pull request #251 from pstaabp/stage4

Stage4