Add getFeatures method to ConfigStateService to get features as object

[mehmet-erim]

getFeatures and getFeatures$ methods will be added to the ConfigState. The new methods can be used as shown below:

const features = this.configState.getFeatures([featureKey1, featureKey2]);
console.log(features) // { featureKey1: featureValue1, featureKey2: featureValue2 }

this.configState.getFeatures$([featureKey1, featureKey2]).subscribe(features => {
console.log(features) // { featureKey1: featureValue1, featureKey2: featureValue2 }
});