Fix RH #633169 again.
https://bugzilla.redhat.com/show_bug.cgi?id=633169

Add a check that was omitted when backporting commit 5d321961

Correctly restore caret position before and after the undo and redo actions.

Correct a typo introduced in commit 9aee4199.

Don't try to use innerHTML as innerText..

Reuse the existing wrapper when inserting a new signature.

This had been reported at
https://bugzilla.redhat.com/show_bug.cgi?id=1352271

Just put the quotation marks on the beginning of the element.

EHTMLEditorView - Redoing a delete operation in a PRE element could wrap the content in SPAN element

There was one case unhandled in commit b962cc71.

It looks like they are not needed anymore and they could prevent the undo/redo
delete operations to behave correctly.

They were just hidden and we could trigger them with a shortcuts i.e.
Control + B made the selected text bold.

Correctly process the block elements to avoid situations when an extra new line
could be added on the end of the block or not added at all. Always look if the
new line is indeed there, if not add it there explicitly.

When removing an image also remove its wrappers and the block where the image
was, if the block is empty after the image was removed.