Initial TopoServReader work: GetKeyspaces.
vtctl UpdateTabletAddrs command.
TopoReader methods: GetSrvKeyspace, GetEndPoints.
FIXME note.
Use a struct as the reply type in Toporeader.GetKeyspaces.
TopoReader is now an interface in topo.
Merge branch 'topoocc'

Conflicts:
	go/cmd/vtctl/vtctl.go