Adding a document watcher

[Jonathan Blandford <jrb redhat com>]

Hi,

While looking into continuous view, I want to make some changes to the
way we handle the current view of the document.  Currently, all the
parts of the viewer (such as find, the display widget, etc.) manipulate
the EvDocument directly.  I'd like to add an EvWatcher widget that can
canonicalize the current viewed document.  This object would just keep
track of the current document, and emit a signal when it changes,
instead of the ev-view doing that now.  I want to do this as we're going
to have multiple views of the document in the future, and it's currently
a little confusing anyway. 

Any objections to me reworking the code to do this?

Thanks,
-Jonathan