games/widelands: Update to release 1.3

Since the release of version 1.2, we implemented several hundreds of new
features and bugfixes; for example, to name just a few of the highlights:

- Market trading
- Six new maps added and three old maps removed
- Economy districts
- Many improvements to the in-game Encyclopedia
- Download website maps as add-ons
- New visualisation modes in the editor
- Many new capabilities for add-on developers

Widelands 1.3 is translated completely into Czech, Durch, German, Hungarian,
and Low German, and the translations for 9 other languages are more than 2/3
complete.
