[#802 state:needs_tests]  make the subdomain case insensitive in the url

Conflicts:
	app/controllers/application_controller.rb
[#802 state:resolved] test for subdomain mismatching case with abbrev  also made uniqueness check for domain abbrev case insensitive
[803 state:resolved] finish tests for grade and end year filtering of multiple enrollments of displayed students
[#803 state:needs_tests] filter enrollments by grade and end_year on the student index page as well