Configurable networkmanager

[dnmvisser]

Fixes #63

[pmeulen]

Hi dnmvisser,

Thanks for your contribution!

First a remark over form: could you please only add the commit(s) that contributes to the feature (i.e. 09fc9a3) to this PR, and not include the other, unrelated, commits? This way it is unclear what will be merged. You could remake your PR and force push the new one (unlike what https://help.github.com/articles/about-pull-requests/ says, doing a force push will work fine in my experience). You could also start a new PR, and close this one.

Regarding the implementation:

• Adding the option to NOT disable the NetworkManager is fine. I think disable_networkmanager would better describe what it does.
• You specify the variable as a boolean, which makes sense IMO. In that case the default() filter is a better fit (i.e. when: disable_networkmanager | default(true)) because then defining the variable with either true or false works as expected.