Consider supporting true/false values for flag parameters by default

[tarekoraby]

Flag parameters are enabled/disabled by either being present or not. That is, flag types default to --<PARAMETER_NAME> when set to true. When set to false, nothing is passed.

If I want to pass a flag with the value false, I will need to use a special version of the pass-as property:

• pass-true-as: --<PARAMETER_NAME>=true
• pass-false-as: --<PARAMETER_NAME>=false

But as the true/false dichotomy is a natural interpretation of flags, we should consider supporting these values for flags out of the box (without asking people to use any special pass-true or pass-false syntax).