_pushProperty(result, name, value) {
		const def = this._propertyDefinitions[name];
		if(! def) {
			result[name] = value;
		} else if(def.handler) {
			def.handler(result, value);
		} else {
			result[def.name || name] = def.mapper(value);
		}
	}
Map and add a property to an object.

@param {object} result
@param {string} name
@param {*} value