Refactor the MaxByte functions to accomodate the DataAvailabilityHeader

[evan-forbes]

As an intermediate step to completing #184, the data availability header was added to the BlockID in #312. Introducing the data availability header dramatically changes the number of bytes in Commits, Votes, and the Block structs, and this fact effects the functions that count the max number of bytes, along with the tests for those functions. Most notably, three tests have been commented out until the BlockID is replaced with the header hash. These tests are TestMaxCommitBytes, TestBlockMaxDataBytes, and TestBlockMaxDataBytesNoEvidence. Not only do these tests have to be uncommented, but the functions that they test need to refactored in order to accomodate for the data availability header when necessary. There should also be an equivalent max byte function/test for the DataAvailabilityHeader.

[evan-forbes]

This DAH is no longer included in the blockID