Unit publishing and button sync up

This PR completes the Unit publishing widget styles (aside from synching up the colors with the WIP outline) and syncs up buttons page level/mast buttons across Studio. 

@talbs Can you review my work here? @cahrens Can you review (once tests pass) to make sure I didn't revert any recent changes?
looks like a lot of the properties you're using here are covered by the ```%cont-truncated``` placeholder (https://github.com/edx/edx-platform/blob/frances/feature/button-sync3/common/static/sass/_mixins.scss#L357). Any chance we could use this instead of duping these same css properties?