Made initializers for both default responses public and added metrics parameter.
Made initializers for both default responses public and added metrics parameter.

This change allows default responses to be rebuilt in client APIs as necessary. Certain use cases would be wrapping up errors in an external error type as well as modifying the data payload for a downstream response handler.

Noobish1/Alamofire,easyui/Alamofire,jschmid/Alamofire,Lomotif/Alamofire,richardPFisk/Alamofire,easyui/Alamofire,iosheadhunter/Alamofire,yimajo/Alamofire,yimajo/Alamofire,Alamofire/Alamofire,antigp/Alamofire,antigp/Alamofire,Alamofire/Alamofire,Lomotif/Alamofire,Noobish1/Alamofire,richardPFisk/Alamofire,Farteen/Alamofire,iosheadhunter/Alamofire,jschmid/Alamofire,Farteen/Alamofire