Monitoring: implement "Security" config tab
Monitoring_ConfigController: make writeConfiguration's parameter `file' non-required

refs #6641
Monitoring config: implement SecurityForm

refs #6641
Monitoring config: use SecurityForm

refs #6641
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
SecurityForm: Add helptext

refs #6641
Merge branch 'bugfix/sensitive-custom-vars-6641'

fixes #6641