Add script to shot tempalte coverage

* Add a script to compare the defined metrics with those used in the
  Zabbix template.

* Add a Makefile target to run the above script.

Makefile

@@ -110,6 +110,11 @@ endif
 query-tests:
 	cd tests ; ./run-tests.sh
 
+# Compare the sample metrics with the Zabbix template
+template-coverage:
+	$(PYTHON) zabbix_templates/coverage.py sample-config/pgmon-metrics.yml zabbix_templates/pgmon_templates.yaml
+
+
 # Install the script at the specified base directory (common components)
 install-common:
 	# Set up directories