Fix several issues with the cite-plugin (handling blockquotes).
Pressing backspace in blockquotes will no longer wrap the blockquote into a div.
Pressing enter at the end of a blockquote multiple times will now create a new paragraph after the blockquote (similar to lists).
When blockquotes and quotes are nested the controls will now show the correct status.
Merge pull request #973 from npomaroli/cite-plugin-54808

Fix several issues with the cite-plugin (blockquotes)