Dglance restapi

Updated to include latest commits 

Ok - there is quite a lot here:

[1] REST API for for mobile apps

[2] Support for multi-site - this uses a context_processor for some SITE settings - that drives the site titles, use of CSS files etc.

[3] Support for extra db driven course information - used in landing page, overview pages and in preview mode.

[4] Support for logon from landing page - institution courses only show up if logged in as a institution person.

May need some code checks and tidy ups - definitely needs testing