SAK-25514 added media query to hide navigation below 800px very basic but a start

git-svn-id: https://source.sakaiproject.org/svn/reference/branches/SAK-25514@134218 66ffb92e-73f9-0310-93c1-f5514f145a0a
SAK-25514 added media query to hide navigation below 800px very basic but a start

git-svn-id: https://source.sakaiproject.org/svn/reference/branches/SAK-25514@134219 66ffb92e-73f9-0310-93c1-f5514f145a0a