Library Content XBlock
High-level tests of content libraries
Made empty course url the 'home' url instead.
Added subheader to content libraries page.
Fixed header display
Added 'Display Name' to Library content module.
Added explanation to container view of Library Block.
Made errors on Library blocks use validate functionality.
Added test for /home/ redirect.
Quality check and test fixes.
Update text on new content library form.
Libraries UI: remove underline on hover.

This changes the style of the inactive libraries/courses tab when hovering.

Only the active tab on the dashboard page gets the blue underline.
When hovering over an inactive tab, the color of the text changes,
but the underline does not appear.