Vagrant: Add Icinga2 and test configuration

refs #6127
Vagrant/Icinga2: Optimize test configuration
Vagrant/Icinga2: Upgrade to snapshots and optimize configuration

refs #6127
Vagrant/Icinga2: Add dependencies for test config

refs #6127
Merge branch 'feature/vagrant-icinga2-core-6127'

Switch core for Icinga Web to Icinga2 package install and add test configuration.

Consider: Run 'vagrant priovion' and remove /etc/icingaweb configuration folder
to install new core and let new icingaweb configuration take place.

resolves #6127