Bug fix -- subcategories in forums topic list should now be sorted alphabetically

Add delete confirmation to static pages.

Allow Studio to display error modules.

Remove network calls in tests

Conflicts:
	lms/djangoapps/courseware/tests/tests.py

Changed error message on failure and made test more robust

Will/use mixed modulestore in tests

Better error message

teardown the content database after tests

We used to use a regular JS `confirm`; this makes the UI consistent
with the rest of Studio.

Payment/Shopping Cart Backend

and add the ability to record the fulfillment time

* Make currency a property of the Order (for validation purposes)
* Remove null=True from Char fields
* Use InheritanceManager for subclassing OrderItem
* Change VerifiedCertificate to better handle some new use cases
* Cleaned out old migrations
* Tests!