Meta-Perspectives

[lucksus]

Add the concept of Meta-Perspectives to the executor which show up as regular perspectives to the UI and can be interacted with in the same way (querying links, prolog queries, subscriptions) but which are just virtual overlays of other Perspectives, Neighbourhoods or even other data sources (DM messages, agent public perspectives).

(could also be called virtual Perspective)

What this enables:

1. Running searches and Social DNA over several Neighbourhoods that don't need to know about each other (we just need the agent have access to all NHs.)
2. Easily searching over many public agent perspectives, like all friends of the agent in order to render a Twitter like update-stream
3. Interacting with DMs through the Perspective interface which would mean existing UI components could be reused for this.

Open question:
What would a write to such a meta-/virtual-Perspective mean? Where would it be saved? How to set-up the connection between such writes and the DM system?