Negate FeatureGateAttribute

[zhiyuanliang-ms]

Why this PR?

#202

Visible Changes

Add Negate property to FeatureGateAttribute and add more constructors for it to allow the following usage:

[FeatureGate(requirementType: RequirementType.Any, negate: false, ["Home"])]

[rossgrambo]

It looks like [FeatureGate("Home")] uses public FeatureGateAttribute(params string[] features)

Could you confirm that there's no weird interaction between
[FeatureGate(true)] and public FeatureGateAttribute(params object[] features)?

I think the generic object parameter might accidently catch the boolean.

[zhiyuanliang-ms]

@rossgrambo

[FeatureGate(true)] will throw exception: Unhandled exception. System.ArgumentNullException: Value cannot be null. (Parameter 'features')

I guess the constructor overload FeatureGateAttribute(params object[] features) has the lowest priority. So we are good here.