Complete conversion of Test API resource to using PK instead of title.
Use file basename as PK.
Fix Test API Resource to allow proper generation of Resource URI.
Change all server side code to process test_id instead of test_title.
Fix client side code to query based on test_id.
Remove colon from "Begin Test:" button.
Merge branch 'nalanda-rct2' of github.com:learningequality/ka-lite into nalanda-rct2

Conflicts:
	kalite/student_testing/api_resources.py
	kalite/student_testing/urls.py
Finish changing over to test_id as test determiner.
Fix testlog fetching for test_ids.
Fix exam mode assignment for test_ids.
Fix Test lists to always return a list.
Merge pull request #2147 from rtibbles/student_test_fixes

Student test fixes