CLC-4478 - Official Sections: As an Instructor, I want to be able to edit official sections

Contains changes related to:

CLC-4525 - Official Sections: Refactor business logic shared between LTI tools
https://jira.ets.berkeley.edu/jira/browse/CLC-4525

CLC-4526 - Official Sections: Create Course Info API end-point
https://jira.ets.berkeley.edu/jira/browse/CLC-4526

CLC-4534 - Official Sections: Add course info option to course provisioning data feed
https://jira.ets.berkeley.edu/jira/browse/CLC-4534
@redconfetti looks like quite a bit of copy/pasting, how about this:

```
<div class="row collapse">
  <div class="medium-12 columns">
    <h1 data-ng-show="tabs.existing">Existing Sections area</h1>
    <h1 data-ng-show="tabs.available">Available Sections area</h1>
  </div>
</div>
```