[Routing] Add an extension-point for DI into the Matcher/Generator Dumpers

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

The Routing's MatcherDumper and GeneratorDumper classes are instantiated very deeply into the Router::getGenerator() and Router::getMatcher() methods. This pull requests aims to separate the instances creation to ease dependencies injection for these classes, as we can't inject dependencies in another way (service definition, compiler pass or whatever).

An example of usage would be the following : https://gist.github.com/gnutix/5844630