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)

bin/__dispatch.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+# This script dispatches invocations transparently to programs instantiated from
+# Nix.
+#
+# To add a new tool, insert it into the case statement below by setting `attr`
+# to the key in nixpkgs which represents the program you want to run.
+set -ueo pipefail
+
+readonly REPO_ROOT=$(dirname $0)/../..
+TARGET_TOOL=$(basename $0)
+
+case "${TARGET_TOOL}" in
+  terraform)
+    attr="third_party.terraform-gcp"
+    ;;
+  kontemplate)
+    attr="kontemplate"
+    ;;
+  blog_cli)
+    attr="tools.blog_cli"
+    ;;
+  stern)
+    attr="third_party.stern"
+    ;;
+  kms_pass)
+    attr="tools.kms_pass"
+    TARGET_TOOL="pass"
+    ;;
+  aoc2019)
+    attr="fun.aoc2019.${1}"
+    ;;
+  rink)
+    attr="third_party.rink"
+    ;;
+  *)
+    echo "The tool '${TARGET_TOOL}' is currently not installed in this repository."
+    exit 1
+    ;;
+esac
+
+result=$(nix-build --no-out-link --attr "${attr}" "${REPO_ROOT}")
+PATH="${result}/bin:$PATH"
+
+exec "${TARGET_TOOL}" "${@}"