Cleanup JMX naming

BTM-104 has shown that multiple BTM instances can end up being registered in the same JMX server. A good example is when you run two web apps embedding BTM in the same Tomcat server.

This can cause subtle problems as the JMX names aren't unique across multiple BTM instances (the two web apps cannot have a similarly named pool for instance) and adds some confusion.

The server ID should be prepended to all JMX names to clearly delimit two BTM instances in a single JMX server.