Allow a feature flag to require all registered feature filters be enabled.

[jimmyca15]

In response to #28.

Combine feature filters with AND

By default, feature filters are evaluated using a logical OR operation. If any feature filter that is registered for a feature is enabled, then the feature is considered to be enabled. This PR adds the capability to customize this so that feature filters are combined with a logical AND operation. This means all registered feature filters would need to be enabled for the feature to be considered enabled.

Configuration

Overriding feature filter evaluation to use AND can be done by specifying the RequirementType for a given feature flag.

RequirementType

• Any: Default. If any feature filter is enabled, the feature will be considered enabled.
• All: Requires all feature filters to be enabled to enable a feature

{
    "FeatureManagement": {
        "FeatureFlags": {
            "MyAndFeature": {
                "RequirementType": "All",
                "EnabledFor": [
                    {
                        "Name": "Test",
                        "Parameters": {}
                    },
                    {
                        "Name": "Test2",
                        "Parameters": {}
                    }
                ]
            }
        }
    }
}

[rossgrambo]

Closing in favor of #221