fixed tabindex

remove cut/paste error which results in a server error.  is not defined ...

remove cut/paste error which results in a server error.  is not defined when there are no assets. Also fix up base.js to only register one set of handlers for file section which gets rid of the multiple file selection dialogs from appearing

catch when users empty out a section name. don't allow them to do that.

Fix/cdodge/pre push tweeks

replaced DateJS with latest version from their repository. There was a known bug about parsing times that are 12:xxPM - believe it or not.

remove the add users button if logged in user is just staff member

Bug/lyla/templates

hide 'View Live' button if no units have been published

optimize slightly, allow caller to pass in the list of units in a subsection, so we don't have to refetch

Feature/cas/tomg/embed links

Polished sign up

Feature/cdodge/edit section info

Merge branch 'feature/cale/cms-master' of github.com:MITx/mitx into feature/cdodge/edit-section-info

improvements on asset upload refresh. Now we don't need to refresh the w...