SecurityForm: replace `customvars' with `protected_customvars'

refs #6641
Vagrant/Puppet: add file '/etc/icingaweb/modules/monitoring/config.ini'

refs #6641
Remove '{{SAVE_ICON}}', tiny design fixes

refs #6641
Monitoring/Object: filter protected customvars

Move the responsibility from the viewscript to Monitoring/Object

refs #6641