Remove redundant check for creates argument.
If force=true, ignore python-apt's advice

This lets you downgrade packages, for instance.
service now detects systemd is actually running, not just installed
Merge pull request #343 from bcoca/service_systemd_fix

service now detects systemd is actually running, not just installed
Merge pull request #124 from jonhadfield/remove-unused-creates

Remove redundant check for creates argument.
Merge pull request #333 from hfinucane/apt-dkpg-downgrade

If force=true, ignore python-apt's advice
Correct variable name
Merge commit '383ecdb' into devel