add support for respondus monitor

Adds the require_lockdown_browser_monitor and lockdown_browser_monitor
data Quiz attributes and makes them accessible through the Quiz API.

Test Plan:
 * With lockdown browser enabled:
 * Should be able to read/set lockdown properties through quiz api:
   require_lockdown_browser, require_lockdown_browser_for_results,
	 require_lockdown_browser_monitor, lockdown_browser_monitor_data
 * if use_lti_tool plugin setting is set (enabled in different commit)
   then the LB options are hidden in quizzes UI

closes PLAT-291

Change-Id: Ic45a4946d5632a01f32709b76ce2907b1141f351
Reviewed-on: https://gerrit.instructure.com/29648
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Derek DeVries <ddevries@instructure.com>
QA-Review: Nathan Rogowski <nathan@instructure.com>
Product-Review: Bracken Mosbacker <bracken@instructure.com>