Optimize CMS UI - redesign sidebar, classes, ontology

[joepio]

Problems with current UI

• Base ontology is a resource in the drive, shown twice, and has the same name as the drive
• It's hard to find all instances of one class
• Classes don't feel like an important abstraction / they are too hidden
• The new instance button in the Class view is confusing, it should probably be removed

Solution

• Show the classes in the sidebar, as collapsible entities in the sidebar.
• Show a search symbol in the sidebar next to the classes. If you press that, show all instances. Alternatively, change the Class view so that it lists all instances.

EDIT: I think the View options from #1058 might be better.