Fix metric names

Created by: hacklschorsch

Fixes #95 (closed).

@exarkun What do I do about materialization? I just changed the materialized nix file by hand, that made it work. I only changed three strings, why is this so complicated

@exarkun Something about shell.nix is funky - it currently requries a ./default.nix that isn't there. Maybe it's supposed to require ./nix/default.nix instead?

nix/materialized.paymentserver/PaymentServer.nix

@@ -11,7 +11,7 @@
     flags = {};
     package = {
       specVersion = "1.10";
-      identifier = { name = "PaymentServer"; version = "0.1.1.0"; };
+      identifier = { name = "PaymentServer"; version = "0.1.1.1"; };
       license = "Apache-2.0";
       copyright = "2019 Private Storage.io, LLC.";
       maintainer = "support@privatestorage.io";