Remove long-deprecated Capability code; deprecate some more

In May and July 2015, i.e. long before WildFly 10, I deprecated quite a bit of code in the RuntimeCapability class and its Builder. None of it is currently used in WildFly Core or WildFly (nor was it used in WildFly Core 3 or WildFly 11.) So, time to remove this code.

Part of what's being removed is Builder setters for non-hard requirements. Being removed because we have no current use cases for that data. Since the setters are being removed, the getters can't return anything but an empty set. So, part of this task is to deprecate the getters for that data so we can remove those later.

I'll also deprecate anything not package-protected about AbstractCapability. It does not need to be visible outside its package, and currently isn't except in some comments.