generic block element

http://redmine.oerpub.org/issues/495

the objective here was to have a default "semantic block" that is activated on things even if we don't necessarily recognize the specific type of the block. right now the selector is all divs that are not ephemera, not editable and not blocks. i also tore through the existing semantic block ui elements and refactored them to use ephemera so they'd be easier to find.

i accidentally a bunch of commits from testing onto my last branch for this and had to recreate the PR with a new branch