test: Validate calls to the sample debos recipes in the README

Add a script to extract the debos calls in the README and run them to ensure
that they can be succesfully run on the SDK.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

test/test-sample-documentation

+#!/bin/sh
+
+set -e
+
+README=README.md
+
+fail () {
+    echo "$*" >&2
+    exit 2
+}
+
+test -r "$README" || fail "Unable to read '$README'"
+
+grep -o 'sudo debos.*' "$README" | while read CMD
+do
+    eval echo $CMD
+    eval $CMD
+done
+
+export SDCARD=./fake-sdcard.raw
+
+grep -o 'sudo bmaptool.*' "$README" | while read CMD
+do
+    eval echo $CMD
+    eval $CMD
+done