scripts/bw-compatibility-test: add backwards compat test

In this commit, a new backwards compatibility test is added. See the
added README.md file in this commit for all the info.

scripts/bw-compatibility-test/execute.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+# The execute.sh file can be used to call any helper functions directly
+# from the command line. For example:
+#   $ ./execute.sh compose-up
+
+# DIR is set to the directory of this script.
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+source "$DIR/.env"
+source "$DIR/compose.sh"
+source "$DIR/network.sh"
+
+CMD=$1
+shift
+$CMD "$@"