Create new group configurations page.

**Ticket**: [BLD-1121](https://edx-wiki.atlassian.net/browse/BLD-1121)

**Acceptance criteria:**
* Button (or something) on the Group Configurations page to create a new configuration. 
* Editable fields appear for: 
  * Group Configuration Name (required, ok if non-unique)
  * Group Configuration ID (READ-ONLY, required, numeric, must be unique within a course - can just increment sequentially for courses with no existing but take into account courses with existing group configurations created in the user_partitions value on Advanced Settings page - we must not overwrite any values.)
  * Group Configuration Description (optional)
* DO NOT show any Groups information on the front end (will be a separate story) but DO create default groups (2 groups, named Group A & Group B, both at 50% allocation) on the backend. (This should already be handled by the split_test module, but we should test to make sure this reflects correctly in the Group Configurations page.)
* Create button should save the group configuration.
  * Error message should appear if required fields are omitted upon save. 
  * User should stay in the New/Edit Experiment modal to correct the error. 
* Cancel link should not save but should close the new group configuration modal. 

**sandbox:** http://studio.olmar.m.sandbox.edx.org/

@andy-armstrong , @cahrens , @frrrances please review.
I definitely think we need more conversations about Jasmine vs. Bok Choy. I agree that Jasmine tests are great for testing things like error cases, as those cannot be done in Bok Choy. But I get very nervous when we are creating mock templates for Jasmine tests, as they are basically impossible to keep in sync with the real templates used to create HTML on the server (Jasmine tests of code using client-side templates don't have this flaw). Similarly, mock responses from the server may not match the real server responses.

I think there is no replacement for integration tests to make sure that all the individual pieces fit together correctly. I personally would be willing to do less Jasmine tests in favor of more bok choy, regardless of what it does to our JavaScript code metrics-- I don't think that should be driving the decision. But so far my Bok Choy tests have suffered from sporadic failures, so that's another point in favor of Jasmine.

In short, I don't think there is an easy answer here. But we should avoid wasting time by double-testing code.