Use filter fn to simplify, sort includes

[henryiii]

Small cleanups:

• Sort includes is now working
• lname and sname have getters
• get_parent works in const settings
• Group printing by CLI::Formatter has been refactored to use filters
• help all printing cleaned up
• Added make_positionals(app) for users to override if desired

[codecov]

Codecov Report

Merging #120 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #120   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          11     11           
  Lines        1647   1646    -1     
=====================================
- Hits         1647   1646    -1

Impacted Files	Coverage Δ
include/CLI/StringTools.hpp	100% <ø> (ø)	⬆️
include/CLI/Validators.hpp	100% <ø> (ø)	⬆️
include/CLI/FormatterFwd.hpp	100% <ø> (ø)	⬆️
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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