1.1.1 - Upgrade to TZDB version 2020c

• 1.1.1 (2020-10-18, TZ DB version 2020c)
  • Add documentation for using the PrintStr<N> class from the AceUtils
    library (https://github.com:bxparks/AceUtils) on the various printTo()
    methods. The string content can be retrieved using the
    PrintStr::getCstr() method which returns a normal const char*
    C-string. The PrintStr<N> class replaces an earlier, unreleased version
    that was called CstrPrint<N>.
  • Add 'Validation Tests' GitHub workflow for running
    tests/validation/*Test.
  • Create blacklist.json file for each compare_xxx tools, to disable
    validation checks for DST or abbreviations due to bugs in the 3rd party
    libraries.
  • Add ValidationScope enum to provide better control over whether the
    DST or abbrev fields are validated.
  • Print better diagnostic messages when tests/validation fails in
    BasicTransitionTest and ExtendedTransitionTest classes.
  • Upgrade target version numbers of 3rd party libraries used for
    tests/validation: pytz from 2019.3 to 2020.1, JDK 11.0.6 to 11.0.8.
  • Upgrade to TZDB 2020c.
  • Restrict GitHub Actions workflow to run just BasicHinnantDateTest and
    ExtendedHinnantDateTest, because the other Python and Java tests break
    every time a new TZDB version comes out.
  • Add DEVELOPER.md file containing notes mostly for myself.