Improve MathAssignment controller and view

Improve MathAssignment Create, Edit, Details controllers  for admin;
Add view for users without admin role.
Add filters for assignment list on view page for users.
Merge remote-tracking branch 'origin/master'

Conflicts:
	MathPro.WebUI/Content/Site.css
	MathPro.WebUI/MathPro.WebUI.csproj
	MathPro.WebUI/Views/Shared/_Layout.cshtml