Refactoring Campaigns

The scripting code of the campaigns should be cleaned up with the following requirements:
* All campaigns should make use of the aux-formatting (http://wl.widelands.org/docs/lua/aux_formatting/). This will give them an equal look.
* No translations should be destroyed. Therefor a script is necessary that will adjust the translation files (remove "--NEW OBJECTIVES--" etc.) (https://help.launchpad.net/Translations/YourProject/ImportingTranslations)
* Some file-naming conventions should be followed. A suggestion is
   - init.lua: initialization and global variables
   - starting_conditions.lua: create the starting conditions (headquarter, wares, workers, etc.)
   - texts.lua: all the objective and speech texts and the speech functions
   - mission_thread.lua: the main mission thread
   - additional files for helper functions
* The scripting directory should be translatable. That would make the quotation marks translatable as desired and an add_objective function could be added to the aux-formatting.