[FEATURE] Routing: Nested SubRoutes
With this change it's possible to load SubRoutes from other SubRoutes.
The syntax is the same as before with two additions:
1. You can specify a ``suffix`` in order to load a SubRoute from
a different file than the default ``Routes.yaml``
2. You can set ``variables`` that will be replaced in the merged SubRoutes
package: 'MyPackage.RestTest' # load SubRoutes from My.Package/Configuration/Routes.Entity.yaml
suffix: 'Entity' # replace placeholder "<entityName>" with "product":