Make sure ids are always send with the same bit-length

[Ablu]

For example the lowering an attribute message takes a 32bit int, the raising a 16bit int for the attribute id.

I think we could maybe do a sendId() function which always sends with either 16 or 32bit and make sure that one is always used. (Maybe it would make sense to introduce a type wrapper for ids so they cannot be mixed with integers anywhere (then we also kill all this unsigned <-> signed randomness)

[Ablu]

Sharing the receive and send code could also help...