Move unused ClockProblem localization to TimeSkew.

TimeSkew is used, but ClockProblem is not. Therefore:
* In English, remove ClockProblem and update TimeSkew wording.
* In other languages move ClockProblem to TimeSkew.
    - In Japanese, use longer text from TimeSkew instead of untranslated
      ClockProblem.
Remove Freetalk from plugins page.

Even with a warning and only showing the plugin in advanced mode, people
are still installing Freetalk and having problems. Because we do not
want anyone but developers who are working on fixing Freetalk installing
Freetalk, remove the plugin for now.

Once the problems are fixed, the plugin will be added again. Even if
Freetalk were not removed, it would still need a new build of Fred to
distribute the fix.
Merge remote-tracking branch 'operhiem1/removeFreetalkAdvanced' into stable-1451
Merge remote-tracking branch 'operhiem1/phrasing' into stable-1451