* Modernize bitfield.cc: Storage changed to vector of bytes, return vector from getRaw, new Span readonly memory view
Modernize bitfield.cc: Code style/review notes
Modernize bitfield.cc: Code format
* Modernize bitfield.cc: Swap end and begin in bit counting code assertion
* Modernize bitfield.cc: Rewrite states and simplify code
* Modernize bitfield.cc: Fixing the code and tests
* Modernize bitfield.cc: Fixing tests
* Modernize bitfield.cc: Formatting; +std::size, +const
Julien