src/vs/platform/configuration/common/configurationModels.ts/ConfigurationModel/addKey
class ConfigurationModel:	private addKey(key: string): void {
		let index = this.keys.length;
		for (let i = 0; i < index; i++) {
			if (key.indexOf(this.keys[i]) === 0) {
				index = i;
			}
		}
		this.keys.splice(index, 1, key);
	}