Smart variables and class parameters improvements


Based on various feedback in FOSDEM, cfgmgmtcamp etc, we are trying to
improve the workflows around parameters usage,
including: global parameters that aren't only strings,
matchers that are arrays (for example domain in ['a','b']) and more.

Before we actually start, we want to make sure we are working on the
right things that you care about, to do so we want your feedback,
first please review our tracker bug at [1], if you have an existing issue
that in your opinion should be linked as well, please let us know.

Additionally, if you ever tried using parameters, and it was too hard,
not usable, not trivial, a whole lot easier with X instead, please
do share, we are trying to build something that is useful and need your

comments, requests, criticism etc are welcomed.

[1] Tracker #4470: Usability of parameters and overrides - Foreman