OpenCS settings

The Subview section is not yet implemented, but I would like people to try it out and provide feedback comments please.  There are some debug statements still in there, please ignore them ;-)

EDIT: now integrated with existing settings code
This is also an internal setting (the local map in OpenMW uses it to disable fog), and not a user setting.
Of course some way to disable fog in OpenCS will be good to have, but user settings are not the correct place. That would most likely be a property of the scene subview (a button to switch on/off there similar to the light modes/visibility buttons).