A Code ID is computed as an MD5 checksum over the actual code, as an
byte[] array.  (Called a MethodID or mid in the code, probably should
be called a 'CapsuleID'.)

A Group ID is computed by taking the (capsule) code ids, sorting them,
and computing an MD5 checksum over it.

A ProtocolID is computed by taking the (code) group ids, sorting them,
and computing an MD5 checksum over it.

Note: A protocol ID can be computed even if only one code group was
transmitted (using DLResponse/DLRequest) because any DLResponseCapsule
contains *all* GroupIDs for the Protocol!

A Method ID is computed by sending a Code ID, its Group ID, and its
Protocol ID through MD5, in that order.  Thus, a method ID describes
a triple (Capsule_i, Code Group_j, Protocol_k).

NOTE: It is the Method ID that is sent in the header of a capsule.
    It is hence the basis for demultiplexing.