Support for namespaced communication

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There are several situations where several apps can reside in the same Tiden runtime. These may be developed by separate teams, and even be located in separate repositories. In this scenario it would be nice if the nouns used in communication are namespaced so that collisions won't occur.

A few requirements for this:

1. Scoping: A namespaced app must be able to communicate with the global scope, and possibly "parent scopes". An idea might be to specify for each app what scopes it should include.
2. The reverse to [1] must be false. I.e., global scope should not be able to make requests to a child scope.
3. Shadowing must be dealt with in an apparent manner. I.e. a namespaced scope should never be allowed to use same noun as its parent scopes.
4. Option to create an anonymous scope. These should be generated at runtime and guaranteed to be unique.

This is a prerequisite for confluence merge based nanos. (edit: name was changed in #1 )