* nix-store --dump-db / --load-db to dump/load the Nix DB.

* nix-store --register-validity: option to supply the content hash of
  each path.
* Removed compatibility with Nix <= 0.7 stores.

src/libstore/remote-store.cc

@@ -185,6 +185,12 @@ bool RemoteStore::isValidPath(const Path & path)
 }
 
 
+PathSet RemoteStore::queryValidPaths()
+{
+    throw Error("not implemented");
+}
+
+
 bool RemoteStore::hasSubstitutes(const Path & path)
 {
     writeInt(wopHasSubstitutes, to);