Don't use ObjectFactory

As Jeremy D. Miller mentions in gregsochanik@dbca91c, you shouldn't use `ObectFactory`, so I've removed it. As I couldn't produce a test that actually failed when removing the whole `DefaultRouteCacheProvider` registration, I removed it completely. If there's a way to force forth the problem in a test, I'd love such a test committed so I could see if there's a way to fix it without using `ObjectFactory`.
Also use a `string.Concat` instead of the `+` operator