* syncing up unit publishing state UI with stateful names/styles
* revising outline item status message display logic to show release status
* fixing publishState value typo in outline UI template
* refining and syncing incontext editor styling
* maintaining visual alignment of collapsed/expanded sections in outline UI
* simplifying page-level action styles on outline UI

STUD-1754

This commit implements STUD-1490, allowing creation of components
on the container page. It also enables the delete and duplicate
buttons now that new content can be created that would benefit.

Note that it also creates shared functionality for adding components,
and refactors the unit page to use it too.

STUD-1306

This is the changes for STUD-1244, which introduces the ability for Studio to display
arbitrarily nested xblocks. In this change, a new container page is introduced which can
display nested xblocks. In particular, the xblock type of 'vertical' is special cased
to be shown inline as a collapsible section. The unit page is mostly unchanged, except
that container xblock's are shown as a link to their container page, rather than being
shown inline.

styling for recursive xblock rendering structure to be used in the container page, pulling from general xblock styles in a separate file.