Grady/ai authoring

Transitioned back to AI grading as a Text box within the Authoring interface, and did the appropriate behind the scenes work (validation, primarily) to make sure that the examples are being proper validated.
Per our hipchat conversation:

**UI text**

In this assignment, you can include example based assessment, student training, peer assessment, and self assessment steps. Select the steps that you want below, and then drag them into the order that you want.

If you include an example based assessment step, it must be the first step.

If you include a student training step, it must precede the peer assessment step.

**Validation error text**

The assessment order you selected is invalid.