Shift configuration into a portable class or struct

[sharpe5]

This means that we can share the same configuration object among multiple Subject. It also makes the internal code simpler, as there are less individual parameters to pass around.

[sharpe5]

Have multiple construtors so it will just work, no matter which way you want to configure the class. Have considered fluent configuration, but I think this style can make the API more opaque.

[sharpe5]

In addition, also add Factory wrappers which make it easy to use with any dependency injection container such as MEF or Unity. Having confif mostly in a class makes this easy.

[sharpe5]

In order to keep consistent with NetMQ, call this property "Options" rather than "Configuration".