Increase performance of getbyname method in router

Because almost all bases on ```Router::getRouteByName``` (for example Url plugin in
views) it is a bottleneck in a
application with bigger set of routes. Each time when ```Router::getRouteByName```
won't find a route in a lookput table, it will try to generate this
table.

I know it's not the cleaniest solution and it can be improved. The best way would be requiring to define a route name while adding it to router.