Accumulated fixes and tweaks

Changed text-method for the zipline. The textprompt to use it will now immediately dissappear when out of the trigger volume.

Added a danger sign in Trollhole, telling the player about minecart danger.

Fixed rolling boulders potentially getting each other stuck in Sourwood.

Reduced the confirmation time for graphical settings down to 3 seconds. Selecting a 'bad' resolution should now revert much quicker back to default.

Fixed a grammar error in Sourwood.