Experimental builder chain idea

This is yet another idea, so we chain "builders" sequentially.

 * Each builder returns a (string) path
 * We specify action to take on `exists` or `not_exists`, i.e. `use`, `create`, err, `exception`, etc.
 * The last builder in the chain is always assigned the Content object.
 * The other routes I guess would be Generic routes? or would they be Route objects?