Clean up leftover rebranding from Zone to Sharing network.  Simplify the links and text on the registration page.  Delete duplicate template.
Link to current video download page from "update"
two more remaining for rebranding
Merge branch 'develop' of github.com:learningequality/ka-lite into template_cleanup
Merge branch 'template_cleanup' of github.com:bcipolli/ka-lite into template_cleanup
Merge pull request #774 from bcipolli/template_cleanup

Develop: Cleanup of (outward-facing) rebranding from "zone" to "sharing network"