[contrib/timezone-gen] Fix timezone gen (#2215)

[contrib/timezone-gen] Fix timezone gen (#2215)

* [contrib/timezone-gen] Move timezone-gen.pl to own folder

* [contrib/timezone-gen] Add fixTzstr

* [contrib/timezone-gen] Add tests and zone data getter
 - tests.pl can be used to verify that the generated timezone conf
   will produce the correct datetimes by testing them against
   what the system's `date` says
 - build-zonedata.pl will download the latest tzdb data and build
   the posix timezone data files. It only builds what is needed
   rather than adding extraneous "right/" and "posix/" timezones.
   FreeSWITCH doesn't seem to be able to use the "right/"
   timezone files.
 - data/ is where the various files needed to generate the
   timezones gets stored