Add null check to getFeedbackResponseForStudent

Also added a test for the null check
Added log message to log null student when getting feedback response
Catch DatastoreTimeoutException in ControllerServlet
[2130] Add missing commit for #1789

closes #2130
changed the accounts used in IHPTest. Added new json files to avoid conflicts while using the same instructor account
Changed btn-tm-action to btn-tm-actions in some html pages
Merge branch 'bootstrap'
Merge branch 'master' into Issue1963
[1963] StudentFeedbackResultsPageAction: Null pointer exception

fixes #1963
Merge branch 'master' into Issue2077
[2077] System exception: org.d

fixes #2077
Merge remote-tracking branch 'origin/master' into Issue2131