Fix ByteSize implementation in regards to IEC specification

[CollinAlpert]

This PR is targeted for the v3 release, since it contains a breaking change in how the ByteSize calculates sizes.

Until now, one kilobyte is considered to be 1024 bytes, which is incorrect. The code Console.WriteLine(ByteSize.FromMegabytes(1).Bytes); prints 1048576 instead of 1000000 which was initially very surprising to me. I have had countless discussions over this surprising behavior with my teammates.

This PR fixes the calculation and adds methods to aid in calculating binary instead of decimal powers.