Made `GetTitle` and `SetTitle` part of Window trait
Made `GetTitle` and `SetTitle` part of Window trait

Closes https://github.com/PistonDevelopers/event/issues/274

caldwell/piston,placrosse/piston,PistonDevelopers/piston,PistonDevelopers/piston,oldmanmike/piston,mitchmindtree/piston,KevinFrans3/piston,bvssvni/event,tempbottle/piston,getynge/piston,Potpourri/piston,bvssvni/piston,bvssvni/piston,axelmagn/piston