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.
ISTM that the convention is to not use the sort prefix on the name of those sorting types, otherwise it becomes too repetitive when you call sort.Sort(sort...)