Adds support for Respondus Monitor

1) Adds require_lockdown_browser_monitor and lockdown_browser_monitor_data attributes to the Quiz model object.

2) Makes the require_lockdown_browser, require_lockdown_browser_for_results, require_lockdown_browser_monitor and lockdown_browser_monitor_data Quiz attributes accessible through the Quiz API.

3) Hides the require_lockdown_browser and require_lockdown_browser_for_results from the New/Edit Quiz pages if the new use_lti_tool setting of the Respondus LockDown Browser plugin is enabled. This requires version 1.2 of the plugin (not part of this repository). Behaves as before if the plugin is not installed, not enabled or a previous version.

4) Provides tests for the new attributes, including making sure they are preserved in course copies and that they can be set and retrieved using the Quiz API.

Test Plan:
spec/models/content_migration_spec.rb
spec/apis/v1/quizzes_api_spec.rb
spec/models/quizzes/quiz_spec.rb