Settings split up into reusable classes

The GameSettings class was removed and replaced with an abstract
Settings class, which has two subclasses: SettingsFromFile and
SettingsFromURL. This structure allows for reusage of the class, instead
of only being available for the main configuration.
The change was partially implemented so that a TiledLevel can be loaded
together with a properties file containing data such as the spawn point,
for example.