Relocate schema to edge_gateway directory

In preperation for renaming to Vcloud::EdgeGateway::Schema::*. I'm moving
them separate to the renaming so that git doesn't treat it as an add+rm.
Rename Vcloud::Schema->Vcloud::EdgeGateway::Schema

So that we don't stomp over the main Vcloud namespace. This matches the
directory move in the preceeding commit.