Add initial support for localization and internationalization

[gcotelli]

• Move LanguageRange and LanguageTag abstractions from Hyperspace to be used in the localization support
• Add string escaping support to ease the creation of strings including control characters and Unicode code points
  • String>>unescaped transforms the escaping sequences into the target Unicode characters
  • String>>escaped is a kind of inverse but some sequences have several possible escaping options
• Add CurrentLocale dynamic variable to control the localization options
• Add string localization support for translating strings in several languages
  • String>>localized and String>>localizedWithAll: providing translation services dependent on the current locale for the process, placeholders between {} are interpolated with the provided arguments, and escaping sequences are automatically unescaped.
• Add extensions to TestCase to ease the testing of locale-aware code

This is the first milestone, in the future we will be adding localized methods for Numbers, Chronology objects, and pluralization rules as needed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (4fea7c4) to head (ae6c6cc).

Additional details and impacted files

@@                 Coverage Diff                  @@
##           release-candidate      #126    +/-   ##
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  Coverage             100.00%   100.00%            
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  Files                     81        95    +14     
  Lines                   7383      8318   +935     
====================================================
+ Hits                    7383      8318   +935     

Flag	Coverage Δ
unit	100.00% <100.00%> (ø)

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