Add Docker documentation to the installation docs; update and create the ”Scripts To Rule Them All” scripts for easy use of the Docker Composer environment.

Fixes #2425.

script/setup

@@ -0,0 +1,18 @@
+#!/bin/sh
+
+# script/setup: Set up application for the first time after cloning, or set it
+#               back to the initial first unused state.
+
+set -e
+
+docker_compose="docker-compose --file docker-compose.yml"
+
+script/bootstrap
+
+script/poll-for-db
+
+echo "==> Setting up DB…"
+# reset database to a fresh state.
+bin/rake db:create db:reset
+
+echo "==> App is now ready to go!"