Drop the engine support

[tagliala]

I'm going to drop the engine support, because it is buggy and the implementation is partial.

A proper engine support should

1. Preserve the engine helper (Putting an engine in a localized block breaks engine routing method #166); and
2. Should not duplicate :locale in paths (Routing spec for Engine #173).

If there is someone that would contribute to this and submit a PR, please make sure that the aforementioned points are checked