Closing template tags por escaping html.

* Closing template tags on nagios templates.
* Reorder on admin.
* Enable django_extensions on settings.py
Change model hardware policy checks, fixed templates for nagios and updates images in doc
Merge https://github.com/tic-ull/arritranco

Conflicts:
	arritranco/monitoring/nagios/templates/nagios/hardware_checks.cfg
	arritranco/monitoring/nagios/templates/nagios/host_ext_info.cfg
	arritranco/monitoring/nagios/templates/nagios/hosts.cfg
	arritranco/monitoring/nagios/templates/nagios/service_checks.cfg