Add support for POSTing multivalued data

Conflicts:
	MKNetworkKit/MKNetworkOperation.m
Support for multivalued key (like http://foo.com/?foo=bar&foo=foo)

Conflicts:
	MKNetworkKit/Categories/NSDictionary+RequestEncoding.m
Added useCookie: method to disable cookie

Conflicts:
	MKNetworkKit/MKNetworkOperation.h
	MKNetworkKit/MKNetworkOperation.m
Added x-body of userInfo when operationFailedWithError.

Conflicts:
	MKNetworkKit/MKNetworkOperation.m
Added limit storage cache cost.

Conflicts:
	MKNetworkKit/MKNetworkEngine.m