Much improved.  Unified the global and class options into a single
option list.  Implemented static and dynamic setting paths as much
as possible.  Dynamic path does require packet/RPC but otherwise
there's near unification.  Dynamic modes can't get values back yet
due to the response/notifier scheme but this doesn't bother me.
Flatten global and class options into simpler struct-like entities.
Setter/getter available on these when needed (external APIs) but code
can otherwise fiddle directly when it knows what to do.  Much duplicated
options/state removed from HttpPolicy.  Comments cleaned up.  Threads
better described and consistently mentioned in API docs.  Integration
test extended for 503 responses with Reply-After headers.