First rough cut of a container page.
Couple more changes
updated container header styling and exposed sidebar back to its location. includes some javascript to render tooltips on overflowed text headers
styling for recursive xblock rendering structure to be used in the container page, pulling from general xblock styles in a separate file.
Merge pull request #2507 from edx/marco/studio/container-view

styling for a generic container view in Studio built on top of base styles for xblocks rendered in Studio. Also includes UX reference template area for unit and container pages.