chore: Significantly restructure folder layout

This moves the various projects from "type-based" folders (such as
"services" or "tools") into more appropriate semantic folders (such as
"nix", "ops" or "web").

Deprecated projects (nixcon-demo & gotest) which only existed for
testing/demonstration purposes have been removed.

(Note: *all* builds are broken with this commit)

web/tazblog/shell.nix

@@ -0,0 +1,11 @@
+{ pkgs ? (import ../../default.nix {}).third_party.nixpkgs }:
+
+let tazblog = import ./tazblog.nix;
+    depNames = with builtins; filter (
+      p: hasAttr p pkgs.haskellPackages
+    ) (attrNames (functionArgs tazblog));
+    ghc = pkgs.ghc.withPackages(p: map (x: p."${x}") depNames);
+in pkgs.stdenv.mkDerivation {
+  name = "shell";
+  buildInputs = [ ghc pkgs.hlint ];
+}