[v3] skew in store class attributes

[d-v-b]

LocalStore has a root attribute, but RemoteStore has a path attribute. I believe they have the same function.

We should eventually pick one name for this, and figure out how MemoryStore fits into the picture. In v2, I have been bitten by the fact that MemoryStore does not have a path attribute, so it would be nice to come up with a consistent API here.

Personally I lean toward "path" over "root" because of the similarity to URL semantics, but we should just pick 1 thing eventually.