Embedded API is confusing re process types

The embedded API has gotten a bit confusing with respect to names and types, primarily the use of the word "server" in a number of placing where the relevant thing could either be an embedded standalone server or an embedded host controller.

Originally I saw this module as just being an internal implementation detail for the CLI, used by the offline CLI feature, but now we've opened it up for use by things like Arquillian's WildFly integration, so I want to clean this API up a bit.

I see two minor breaking changes needed:

1) The HostController interface has an odd "public HostController getHostController()" method that logically would only return 'this'. I could keep this but it's not needed and I'd rather get rid of it.

2) The HostController interface's start() method does not throw a checked exception, while the equivalent start() on StandaloneServer does. To do anything coherent I need to unify the exception handling. HostController is extremely unlikely to be used outside wf core, while StandaloneServer is used, and removing a checked exception from StandaloneServer would be a breaking change or any user that catches it, so instead I will add the exception to HostController.start().