Unfinished fromArray methods

[va5ja]

Normally you would of course use fromStream but in case you want to use fromArray you just won't come far.

Let's say you generate files for https://github.com/google/openrtb/blob/master/openrtb-core/src/main/protobuf/openrtb.proto. For example BidResponse::fromArray($array); will crash since $message->addSeatbid($item); expects a SeatBid object but the method gives an array.