Add more number output formats

[tiffany352]

Adds to frac and to sci to explicitly force the use of these representations. Also adds to eng which behaves similar to the default behavior, except rounds to every third power of 10 instead of every power of 10. I might make the output format configurable and set the engineering one as the default in a future version.

While working on this I found a bug in the current version of rink. surveyfoot to digits is incorrect by 3 orders of magnitude. I fixed that in this PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.79%. Comparing base (c0aadc4) to head (f4eea03).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #180      +/-   ##
==========================================
+ Coverage   76.09%   76.79%   +0.70%     
==========================================
  Files          41       41              
  Lines        7383     7425      +42     
==========================================
+ Hits         5618     5702      +84     
+ Misses       1765     1723      -42     

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