Studio: styling revamped course outline-related UI

* adding in outline-related color values
* styling for publishing states
* light styling abstraction for specific outline and unit/container contexts
* revising add item to outline button styles
* adding a few bells and whistles (hover states and error pulsing)
Studio: revising draft/unscheduled item status in outline UI
Studio: syncing up page-level action button classes/styles
Studio: revising in-context title editing markup out outline UI
addressing PR feedback