Improved user & group integration + added more options

Note that this is a major upgrade because it drops support for ubuntu trusty & utopic and also for debian wheezy as it includes changes to systemd (which was not included in those versions).

If anyone needs support for that versions can use the version < 2.0.0 or make a PR adding support for all the distributions using different playbook files, so feel free to make a PR if that's the case 😃

Thanks to @aarnaud for the changes 😃