DOM tool is not ever unregistered from the window document

[mrennie]

CF 0.3a11 + FB 1.10 + FF 12

When the DOM to is registered to attaches itself to window.document. When you disconnect the client and the tool is unregistered it does not detach itself from window.document

Steps:

1. start FB + FBTrace
2. connect client activating the DOM tool via the handshake
3. DOM tools spews onDomMutate events (OK) - can see the entries in FBTrace also
4. disconnect client, check FBTrace, DOM tool is still spewing events (BAD)

[mrennie]

A suggestions from Steve Roussy on http://code.google.com/p/fbug/issues/detail?id=3353:

We should also have something that says "Start sending DOM mutation events for this context_id". And similarly, one to stop them. The client might want to watch only two out of ten tabs, for example.