Sort terms drop-down lists by start date

Terms are easier to select when they are sorted consistently.

Test Plan:
* Create 3+ terms in a different order than their start dates
* Verify terms are sorted in chronological order by start date:
  * `/account/###` *(right sidebar under Course Filtering)*
  * `/account/###` *(click Add a New Course; in the dialog)*
  * `/account/###/users` *(right sidebar under Choose Term)*
* Terms should be sorted the same way as the drop-down list in:
  * Course Settings > Edit Course Details

---

*NOTE: We have a signed CLA for all of Simon Fraser University (SFU) on file.*