Change semantics of viewChange() on MuxChannel

Multiplexer needs to override viewChange(), where the the view is the view of all hosts which have the application ! Example: H1:A1,A2,A3; H2:A3, then A3 gets a viewChange(H1,H2) and the others, A1 and A2 just get a viewChange(H1).

This is a semantic change to MuxChannel. A view received this way basically means "a list of all hosts on which my application (e.g. A1) is currently running. When an application goes down, or is started, then a new view change will be sent to the applications of the same type, e.g. all A1's.

This also affects the determination of a coordinator:

• Issue: H1:A2,A3; H2:A1,A2, coord for A1 is H2, and for A2 it is H1. This is different from the JGroups coord, so we have to tweak MuxChannel?.getState() if and only if the address of the coord is null, then we determine the coord to be the application level coord.

If a client wants to get a list of all nodes in the current cluster, we may have to provide a new method in MuxChannel.