simplify support for managing multiple node processes

[tjanczuk]

This is to

1. pre-create the configured number of processes per application when the first message arrives; change the default to 1
2. allow dynamic determination of the number of processes to create based on the number of processors on the machine
3. use round robin dispatching for subsequent messages

[tjanczuk]

1. Replacing iisnode/@maxProcessCountPerApplication setting with iisnode/@nodeProcessCountPerApplication. This controls how many node.exe processes will be activated per each node.js application. Default is 1. Setting it to 0 will default to creating as many node.exe processes as there are processors on the machine. Processes are created when the first message targeting the application arrives.
2. Messages are dispatched to processes using round robin logic.

[compulim]

Why this option is not default to 0?

[tjanczuk]

Most iisnode defaults attempt to optimize the development experience and should be changed for production (e.g. debugging is enabled by default). Presumably troubleshooting one process instead of several during development provides a better development time experience.