Abandoning the notion of 'observer context'...

As used currently 'observer context' is a call router for 'log' and 'error' calls that may occur outside the normal call scope of app logic (e.g. at load time, or in response to a button click, request completion etc. etc.

The naming 'observer context' is problematic however. So I've renamed the concept 'backchannel' and promoted it to ONMjs-core _even though core doesn't use it at all_... The reason to stuff it in core is because it's tiny, and because I want it available to other library and app code w/only a dependency on ONMjs core.

'backchannel' is suggestive of the purpose, backchannel.log backchannel.error are easy to type and concise.
Shore up move to Encapsule.code.lib.base.BackChannel...

... All the ONMjs observers still refer to 'observerContext' everywhere. The little test program in the tests directory works however as I've just changed the name, not the interface, of the class. But for consistency I'm going to go in and scrub the references to observerContext.
Rename 'observerContext' 'backachannel' everywhere.
Rename the 'canary' observer to 'generic test'