Benchmark Serialization Footprint

[rheitjoh]

Math has support for binary serialization of representations.
It would be useful to measure the footprint of this serialization for different cryptographic objects.
This could then be used in the release paper and to compare the serialization size with other libraries.

[JanBobolz]

One idea here was also to add a "how many elements were serialized [and hence, probably, sent over the network] for each group" counter to the DebugBilinearGroup.