Datasource Explorer component

[josephjclark]

To support magic functions, we need a new panel in the Job Editor that shows all the magic stuff.

The datasource explorer should show:

• Basic documentation for how to access code assist
• Whether magic metadata is available
• An indented list of all the entities in the datasource (really simple visualisation)
• When the metadata was last generated
• [maybe later] A button to update the metadata

This should be displayed in a tabbed panel alongside the existing adaptor-docs component

[josephjclark]

Reduced the estimation for this because a lot of work had already been done - so this ticket is really to integrate into lightning and polish up the UI (which is the risky bit)