Update for 5.0 branch (form for multiple adding of assessments added, constant TEACHPRESS_TIME_LIMIT added, small UI improvements, some UI interface functions splitted). This is teachPress 5.0alpha8.

git-svn-id: https://plugins.svn.wordpress.org/teachpress/branches/5.0.x@974407 b8457f37-d9ea-0310-8a92-e5e31aec5664