#18 Ability for a model request to be directed to specfic server

[Michael Nash]

Currently, when a model request is submitted via JMS,
the first available server picks it up and responds. In a
clustered deploy, it might be necessary in some cases
to direct a request to only a specific server. This
should be easily handled by a request attribute
specifying the server name, as each server in the
cluster is identified by a unique name (which is sent
back in the model response now, BTW)