Using 'world' as scope for many settings rather than 'client'

This adds scope: 'world' to many settings that are concerned with fine-tuning the ping. This gives the GM full control of how the pings will look but consequently reduces the players ability to customise them. In return it also allows for setting up the settings for each world so it can be tailored to the individual world. This would fix #24 and #10 as well but prevent #13 from being implemented. All in all I think this has more advantages than disadvantages as it gives the GM more control over how pings should behave and reduces the amount of settings players have to deal with. #10/#24 and #13 are mutually exclusive anyway so a decision would have to be made and there seem to be more people in favour of the GM being able to select the image than the other way around.

Also the if statement in (what is now) line 158 could be removed if the scope would be set to world as well since players cannot change world scoped settings. I did not see the need to include this here however.