go/zodb: open.go -> storage.go

It is already not only open code there, and we are going to add more
storage wrapping functionality into storage (IStorage wrapper over
IStorageDriver). Storage.go thus seems to be a better name.

go/zodb/open.go → go/zodb/storage.go

@@ -18,7 +18,7 @@
 // See https://www.nexedi.com/licensing for rationale and options.
 
 package zodb
-// open storages by URL
+// IStorage wrapper + open storage by URL
 
 import (
 	"context"