Add more fine-grained RoutePrefix control

[Dresel]

From issue 48:

Atm when AddCultureAsRoutePrefix is used, the prefix is always added at the beginning of the route. This should be configurable:

Before [RouteArea], [RoutePrefix], [Route] - (as it is now) After [RouteArea] but before [RoutePrefix], [Route] After [RouteArea], [RoutePrefix] but before [Route] After [RouteArea], [RoutePrefix], [Route]