New model template for nagios services.
Some improvements on README
New model for service templates.

* Schema migration
* Data migration for 2 starting templates: generic, active and passive services.
* New url for download cfg file on nagios. /monitoring/nagios/getchecktemplates
Fix search on taskstatus and some logging.

* Fixed custom admin filter by status on TaskCheks
* Added some loggin con update_status method connected to post_save signal.
Merge branch 'hot-fixes' into nagios_services_tempaltes
Fixed merge
Refactor freshness_threshold  field.

* Created datamigration to fill defaults on passive-service template
Fix disable active checks on passive service check template.
Fixed templates and some fields.

* Fixed template hardcoded "use" option on checks.
* Moved conversion of NagiosCheckTemplate to dictionary from the view to the template.
* check_command field now optional
* Some data migration
Fixed to avoid conflicts
Merge branch 'master' into nagios_services_tempaltes
Fixed some data migration
Migration for Nullable check_command field.
Fixed machine service interpolated checks on template.
Stupid fix
Fixing True and False values on template.
Migration to delete deprecated field. Add new nullable one