TinyMCE: improve the way wpViews work. Add two paragraphs and capture the caret in them on clicking before/after/left/right of a view or moving the caret with the arrow keys, then show a "fake" caret.

This makes it much more "natural" to move the caret with the arrow keys and to add paragraphs before a view when it is the first element or after a view when it's last.

Props avryl, see #28595.
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git-svn-id: http://core.svn.wordpress.org/trunk@28782 1a063a9b-81f0-0310-95a4-ce76da25c4cd