Game data configuration

[spassvogel]

Game data (such as cost of buildings and yielded resources) should be configurable. Perhaps through a configuration XML or JSON.

[spassvogel]

Structure cost, build time, maximum amount of citizens and revenue is now configurable through a json file. See:

src/main/config/structureproperties.json

Note that only the revenue is actually used at this point.

Important

The way it is implemented now, the file is read and parsed at every poll request for every structure (!!). This is obviously a performance issue that has to be resolved later. I suggest this information has to be read during server startup and stored in the application cache or something. For now it works. If anyone wants to do this, be my guest