* Directly create an array/bitmap store based on the count of bits
* Use u64 words to count bits and enumerate bits
* Store in little endian, then just fixup any touched words
* Only use unsafe to reinterpret a whole bitmap container as bytes, everything
  else is safe
* Allow adding bytes up to the last possible offset

we can setting an initial value in that case

Speed up from_bitmap_bytes, and use less unsafe