Support binary calendar types with tick units other than seconds and milliseconds

[mbeckerle]

Currently DFDL binary timestamp representations are limited to 'binarySeconds' and 'binaryMilliseconds. Other 'tick' intervals have been observed in the real world, for example:

Windows FILETIME - 100ns
OPC-UA protocol - 100ns.

It would be useful for DFDL to be able to handle any 'tick' interval.

It would also be useful for DFDL to allow any length of binary timestamp - currently the lengths are fixed depending on the representation.

The other variable is epoch, but DFDL already allows the epoch start to be specified in a sufficiently flexible way.

These should be considered as candidate improvements for DFDL 2.0.

[mbeckerle]

Note: When creating a DFDL schema for NTP messages, there was a specific issue having to do with signed/unsigned integers being usable for creating seconds or milliseconds.... don't recall exactly, but this needs to be revisited to inform this issue.