L10N Utility

- Combined three l10n utiity scripts into one, which can now do the following:
  - Automatically locate all the localized string files.
  - Look for missing strings in the localized string files.
  - Point out strings that are not used in the code.
  - Count strings.
  - Warn when strings are unchanged across languages.
  - Exit with a status code, so it can be used in unit tests.
- Thanks to Wim Schuermann and Fidel Mato for providing code and ideas.
Merge branch '2.3.0' of tasktools.org:task into 2.3.0