Endianess refactoring:

* Changes for a better form of endianess support.
More endianess refactoring:  field_byte_offset is now called field_start_byte
Finalized framework for field bit order support:

* Note that the name "endianess" was replaced with "bit order" since
  that's what's really being supported here.

* So far, only most significant bit first protocols are supported, but
  the infrastructure for supporting least significant bit first
  protocols, or mixed protocols are not far off.