Iframe reload optimizations for various xblock related actions. Added some improvements related to scrolling to the current xblock. Fixed behavior of the xblock action dropdown list.
The enables opening a Library Content page within the new Studio unit page. This page displays the xBlocks from the specified library and provides basic configuration options for the library.
This is part of the effort to support the new embedded Studio Unit Page. It includes changes to the CourseUnit component and the functionality of interaction between xblocks in the iframe and the react page.
The following events have been processed:
* delete event
* Manage Access event (opening and closing a modal window)
* edit event for new xblock React editors
* clipboard events
* duplicate event
