Refactor views into multiple files prior to developing edit item features. Also changed the edit/create item urls.

Refactor the ViewsItems view, which covered the view and edit table, into a separate (non-view) class under tabs/view_and_edit_table.py. When ready, this will plug straight away into the new tabbed page functionality - in the mean time there is a place holder view to display the view where it used to be found.

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).