Add uuid to saveable_multiple_choices table.

- Add uuid to saveable_multiple_choices table.
Add uuid to saveable_multiple_choice_answers table.

- Add uuid to saveable_multiple_choice_answers table.
Add uuid to saveable_multiple_choice_rationale_choices table.

- Add uuid to saveable_multiple_choice_rationale_choices table.
Add uuid to saveable_image_questions table.

- Add uuid to saveable_image_questions table.
Add uuid to dataservice_blobs table.

- Add uuid to dataservice_blobs table.
Add uuid to saveable_image_question_answers table.

- Add uuid to saveable_image_question_answers table.
Refine default data creation.

- Add data for learners.
Refine default data creation.

- Create learners and record their response.
Add rake task to create default learners.

- Add rake task to create default learners.
Add limit to uuid column in resource_pages table.

- Restrict uuid to 36 characters.
Merge branch pull_request_04_04_2013_a

- Merge branch pull_request_04_04_2013_a into
  test_cleanup_04_02_2013_a
Refine feature test.

- Remove data stuffing from background step.
Refine feature test.

- Remove data stuffing from background step.
Revert changes.

Create an external activity in background step.
Refine feature test.

- Remove student answer data creation from background step.
Refine feature tests to work with default data.

- Refine feature tests to work with default data.
Refine default data yaml.

- Record student response for Atomic Energy investigation.
Merge branch test_cleanup_04_02_2013_a

- Merge branch test_cleanup_04_02_2013_a into
  pull_request_04_11_2013_a
Fix feature test for external activity.

- Fix feature test for external activity.
Fix feature test for searching investigations.

- Fix feature test for searching investigations.