Socket based communication between ServerManager and ProcessManager

Default communication mechanism between SM and PM is via stdio. This should almost always be fine, since we use the jboss-stdio lib to capture application usage of stdio and preserve the original streams for our own use. But there is a slight possibility that an extension module running in the SM will use JNI, which can pollute the stdio streams.

So, we need an option to allow users to configure SM-PM communication via sockets. (The same issue applies for Server-PM and Server-SM communication, but there the SM can parse host.xml and get configuration from it, so the details are different from this SM-PM use case.)

Tasks:

1) Put SM-PM communication behind an abstraction
2) Implement stdio-based and socket-based versions of the abstraction
3) Modify process manager module to accept PM socket configuration via command line params
4) PM passes it's socket configuration to SM via command line when it starts PM
5) Decide how to configure SM's socket – via host.xml? (Note SM needs a socket for communication with the DC – use that?)