hid expects the 'dashboard' reverse url to point to the index page - so leave it that way. Added an initial dashboard called 'main' as that is execpted to exist, and tests require it.

Implement a dashboard infrastructure to allow us to register widget types, create dashboards, create instances of widget types with specific configuration and associate those with a given dashboard, at a given position. The dashboard infrastructure is moved out of hid and into it's own application as it is stand alone (the widgets may depend on hid specific logic, but the infrastructure doesn't).