TypeAwareDocStore.__init__ should not clone mirrors

[mtholder]

I put in logic to clone the push mirror in the wrapper around a phylesystem shard a long time ago to make it easier to bootstrap the phyleystem-api. But that was a mistake. It makes much more sense to just have a helper script that can be called to do this bootstrapping. That would then lead to much less configuration being required to use the phylesystem wrappers.