Allow widgets to display error messages in the front end by raising a WidgetError (while other exceptions only display a generic message so as to avoid potential security leak)

Ensure dashboard displays error in case of missing or faulty widget, rather than causing the whole application to fail.

Use django_assets to manage our assets and ensure we can minify js/css, compile less files, and merge all js/css into a single file. For this to work in production, all assets must be statically defined in his/assets.py. To ensure the correct js/css is included, views can invoke hid.assets.require_assets which will raise an exception if the asset is missing. This also has the advantage of making clear which part of the code depends on a given asset. The admin command in django_asset library's latest release does not work with the latest Django - so we use a version pulled from git. See https://github.com/miracle2k/django-assets/issues/52

Change from using an i tag for icons (which is what sb admin and bootstrap used to do) to using span tags for icons (which is more correct, and what bootstrap3 ended up doing as well)

-- changing icon on basic-text-widget
-- adding active state bg-color to sidebar

Add bootstrap markup to the simple text widget, and add the basic dashboard css. This should be updated when we merge in the theme.

Add bootstrap markup to the simple text widget, and add the basic dashboard css. This should be updated when we merge in the theme.

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).