Downtime support in pynag.Model and command line utility

CLI Usage:

# List downtimes
pynag downtime --list [where host_name__contains='.com']

# Schedule new downtimes, works for hosts,services,hostgroups,servicegroups
pynag downtime where host_name=localhost
pynag downtime where hostgroup_name=webservers --comment "Scheduled maintainance on all webservers"
pynag downtime where service_description__contains='vmware' --comment 'Downtime on everything that is vmware'

# Remove a single downtime:
pynag downtime --remove where id=100

# Remove all downtimes matching search filter
pynag downtime --remove where comment="Scheduled Maintainance"

Pynag.Model usage:

h = Host.objects.get_by_shortname('localhost')
h.downtime(comment='test', recursive=True) # Also downtime for all services