Support `bits` wider than 64 bits

NovAtel's [`RANGECMP`](https://docs.novatel.com/OEM7/Content/PDFs/OEM7_Commands_Logs_Manual.pdf) (pp 842-844) record contains a 192-bit bitfield.

[GPS subframes](https://www.gps.gov/technical/icwg/IS-GPS-200M.pdf) are defined as 300-bit sequences.

RTCM defines some wide bitfields which -- even more problematically -- contain 64-bit integers that are not aligned to byte boundaries.

Emboss should support `bits` of arbitrary size.

Note: the restriction that individual integers within those fields are no more than 64 bits is a separate feature that should be evaluated and implemented on its own.