Create basic gettext infrastructure and French language stub.
First attempt at getting .mo files working with windows (wine).
Add Russian stub translation.
Add more gettext calls.
Add German translation.
Fix compile problem on MinGW and force UTF-8 as encoding.
Use application resource path to locate the translation files.

The late initialization does prevent some of the early functions from
being localized (e.g. the command line help).
Allow localization to be enabled/disabled by configuration settings.

This is only the logic to check the settings, no GUI.
Changing the setting requires a restart as disabling localization simply
skips the call to bindtextdomain() at the application start.
Fix library references and translation scripts on MacOS.
Handle the MacOS application layout when finding resources.
Fix compilation of test cases.
Handle resource layout on linux and add translation files to openscad.pro.