validations in registration form
User Roles.
changed the home.html to StudentHome.html
	new file:   home/templates/StudentHome.html
Added the ExamCellHome.html for the ExamCell Control panel
	new file:   home/templates/ExamCellHome.html
slightly modified the mainbase.html template
	modified:   home/templates/mainbase.html

Added user roles
	modified:   home/views.py
deleted several files