Outbailment id sort

This PR adds the sorting of []*OutputReq by OutBailmentID. It also adds explicit modelling of the OutBailmentID as an 'sortByOutBailmentID' seemed confusing without any definition of what an OutBailmentID was.
Heh, I actually had an OutBailmentID pretty much like this in the first implementation, but then I got rid of it because it was not necessary. I wonder if it's really worthwhile having it, as we could just as well have a outBailmentIDHash() method on OutputRequest