Add scope to `lithium\net\http\Router` and `lithium\net\http\Media`.
- Routes can be scoped using the following notation:
  Routed::scope('); // Returns the current scope
  Router::scope('name'); // Use a new scope
  Router::scope('name', function(){/* executed inside the scope */});
  Router::attach('name', array(), array()); //Attach a mount point to a scope
  Router::attached('name', array()); //Returns the attached mount point configuration
- The Media class can be scoped using the following notation: (i.e. usefull for CDN or others media location).
  Media::scope('); // Returns the current scope
  Media::scope('name'); // Use a new scope
  Media::scope('name', function(){/* executed inside the scope */});
  Media::attach('name', array()); //Attach a mount point to a scope
  Media::attached('name'); //Returns the attached mount point configuration
- Modifiying the Media::webroot() signature (BC Break)
- The paths of assets paths now called 'paths' for consistency see `Media::_asset` (BC Break)
Change `action\Request` behavior.
- `$_GET['url']` is no more supported.
- `action\Request` instance are now initialized using env globals if the option : `['globals' => false]` is not set.
  this mean `$request->env('HTTP_HOST')` is now directly accessible via `$request->http` for example.
Merge commit 'a318a30aec4ffbd19b0605ba2a7c35fc4844063d' into patch/router