* error modules now hidden via access control
* get_module() returns None if user doesn't have access

* All access control logic is now in access.py
* It exports a single method for general use: has_access(user, object, action)
 - possible actions depend on object type (e.g. 'see_exists', 'enroll', 'staff')
* Removed DARK_LAUNCH feature flag--it is now the default behavior
* Replaced check_course with three separate more focused functions that use has_access

Minor things:
* note on using pdb in testing
* moved time parsing helper into timeparse.py
* x_modules now have a .start attribute (None if not in metadata)

Wiki pages can now be viewed from the course URL and the course nav is shown. It doesn't follow the user yet.

Created copy of main.html that is django template. Using this for wiki instead of converting every view.

window, add xqa modal window, add xqa_key to course metadata

* bodyclass block got accidentally deleted

* dashboard links to gradebook and dummy grade summary page

* don't display thousands of '%' characters
* s/percentage/fraction/, since that's what it is

* use url_name to compare to passed params
* remove unused fields from template context
* Also make it possible to link to a chapter