Move all noid generation into separate file

- Adds new file exclusively for computing a noid suffix from a
  template and sequence value
- Simplifies suffix generation algorithm by storing generation state
- Breaks up generation testing better
- Minter is now a wrapper around a generator and a template
Make SuffixGenerator.ToString public

Converts toString => ToString to make it clearer this is part of the
public API
Use uint64, not int64

OOPS
Add maximum sequence computation