[feature] Add openwisp-monitoring

[nemesifier]

Blocked by #214.

• add openwisp-monitoring
  • add celery beat
  • add influxdb, would be great to allow changing the default password easily by just setting it in the playbook
  • add celery task routes for the network queue (related to [bug/change] Fix SynchronousOnlyOperation: change worker settings #242):

'openwisp_monitoring.check.tasks.run_checks': {'queue': 'network'},
'openwisp_monitoring.check.tasks.perform_check': {'queue': 'network'},

The module will be enabled by default, but it should be possible to disable openwisp monitoring with a variable, like we do for openwisp-network-topology.

[nemesifier]

Additional info:

• for installing influxdb, we can use https://github.com/openwisp/ansible-ow-influxdb

[nemesifier]

This feature is available in the dev branch.