Mode 1735 - Updated remove behavior involving federation

[hchiorean]

Several aspects were implemented/changed:

• removing federated nodes or their ancestors does not propagate all the way down to the connectors and the external nodes
• for a connector to get the removeDocument notication, a node.remove() has to be performed on an external node.
• added cleanup around the federatedSegments section of federated nodes and in the system area which stores the projection mappings
• added a FederationManager#removeProjection method which only removes a federated segment from a node, without affecting any of the external content.

[rhauch]

Rebased and merged into the 'master' branch.