Make imports into the CMS ignore broken modules, while still loading bad xml as error modules in the LMS

Switch from exception logging middleware to a django signal handler, so that we no longer swallow Http404 exceptions and turn them into 500 errors

Move vendor javascript into common/static/js/vendor, so that they can be shared between the CMS and LMS, and create an html template that includes all of the vendor js needed for the courseware

Split out code to replace /static urls in get_html into a separate module so that it can be used in CMS previews

Uniquify js fragments pulled from XModules, and load both XModuleDescriptor and XModule js into the cms

Add tests for the edit page for the toy course, and make sure that exporting to github sets up the git repo properly

* connect up views from student app
* Add initial @login_required decorators on the protected views
* Add tests for some of the basic functionality

* NOTE: successfully running the tests depends on an updated version of
  django-pipeline, which fixes a unicode bug (https://github.com/MITx/django-pipeline/commit/efaba4ac63bc635da6a728603e87e14758541ec7)

Config changes:
* Use separate db for the cms
* Run collectstatic before running tests--needed to get everything in the right place for loading pages
* fix some paths related to this
* Turn off JS compressor for CMS
* add empty test_root/uploads dir

Code changes:
* Add cms tests to check that home page and signup pages load
* Add cms account creation test
* Make github sync tests clean out repo dirs before running.

* Enable account creation
* Some code cleanups
* Fix access to nonexistent fields in the account creation view
* Formatting fixes

Don't depend on the mitx directory being named that, so that tests will run in jenkins where mitx is checked out as workspace