* Explicitly define `mode` in relevant tasks.
* Explicitly define the `nginx` `apt_repository` filename in Debian based distros.
* Building OpenSSL from source should now work properly in CentOS 8.
This fixes a bug when only the license is deleted, making system updates fail since the NGINX Plus repository is still within the repositories list yet there is no license to authenticate to the repository
* Added variable nginx_plus_linux_families: ['Alpine', 'Debian', 'RedHat', 'Suse']
* Added variable nginx_plus_bsd_systems: ['FreeBSD']
* Added variable nginx_freebsd_extra_packages: ['security/ca_root_nss']
* Installation of Linux moved to install-plus-linux.yml
* Installation of FreeBSD moved to install-plus-bsd.yml
* Installation of nginx_freebsd_extra_packages moved to tasks/prerequisites/setup-freebsd.yml
* Installation of NGINX Plus tested with FreeBSD 12.0; Lint passed
