Adding functional form of Type printout

[henryiii]

This allows sets to capture and print out the current contents if they have changed. Public API is the same. Fixes #113 part 2.

[codecov]

Codecov Report

Merging #116 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #116   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          11     11           
  Lines        1644   1643    -1     
=====================================
- Hits         1644   1643    -1

Impacted Files	Coverage Δ
include/CLI/Option.hpp	100% <100%> (ø)	⬆️
include/CLI/App.hpp	100% <100%> (ø)	⬆️
include/CLI/Formatter.hpp	100% <100%> (ø)	⬆️

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