[WIP] Rewriting Routing Component docs

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | yes
| Applies to    | all
| Fixed tickets | -

The Routing component was very unclear to a lot of people (including myself). I can imagine that, because the article didn't had a single line of code.

After a lot of help from @dbu on IRC some weeks ago, I finally understood the principles. I decided to rewrite it to make it more clear.

What I've done is doing it a bit more like we do it on the core. Lot of code examples and almost none 'take a look at the source code'. I believe that's the difference between a good or a bad doc.

This is still in a very early stage, my plans:

 - [ ] Finish the rewrite
 - [ ] Document all features included in the component (don't have any "look at the source code" in the article)
 - [ ] Split the article in multiple articles (long articles are demotivating): ChainRouter, DynamicRouter, NestedMatcher
 - [ ] Document new Compiler Pass
 - [ ] Lot of review work (I'll be pleased if you help me with this)