Add initial support for "foreground" command

This is mainly for the benefit of Chromebooks who have a chroot'ed emacs that can run on the main display window. When enabled the /foreground command will make emacs pop up in the front of the display without an edit buffer when there is no text area in focus and the button is clicked.
edit-server.el: fix up my own name
xmlcomms.js: fixed up the foreground message handling

The previous method using the persistent tab connection has a few
problems. The principle failure was when there was no content script
to talk to. As the call is asynchronus we need to check for failure in
the callback which is only possible using sendMessage().

Also some clean-up of the tabs that seem to have sneaked into the code.
edit-server.el: add a edit-server-foreground-frame parameter to any frame
we create as a result of a foreground request.