Made msgs editable, can now correct typos real time

Using html 'contenteditable=true' messages can now be corrected and the
ensuing correction sent live to all recipients. The msg is also saved so
the correction is permanent.

Will see how this plays in the wild. There are a couple of ways to kind
of hack this which is cool, but I'd like to add a way to input html tags
to update images if necessary, and also add some kind of signifier that
a msg has been edited. Not bad for a quick session.