Removing useless line in ClassHandlerManager destructor
Refactor: Using `priv` idiom in ClassHandlerManager to ease the
responsibility of maintain ABI compability in future versions.
Refactor ClassHandler{Manager,} includes to follow Tufão's coding
conventions.
Using consistent IID in ClassHandler
Refactor: context has a transparent usage and "works" on nested
environments.

* Refactor ClassHandlerManager::handleRequest to use less nesting
  and easier-to-follow logic
* Removes context information from HttpServerRequest
* Refactor ClassHandlerManager::handleRequest to show a namespaced
  url to its handlers, then they won't be able to know whether
  they're running "inside a context". Great for nesting. The other
  option would be a stack of contexts instead.