Performance Improvements

• Optimised cockpit screen display when screens are not displayed on screen.
• New option available to control cockpit screen update frequency.
• Tweaked CPU thread priorities to reduce interruption of frame critical threads.
• Optimised loading system to reduce overall loading times.
• Optimised heavy airport scenes impact on CPU.
• Reduced the amount of GPU overdraw to improve GPU performance.
• Memory optimisations to reduce software memory footprint and improve performance on limited memory computers.
• Overall performance optimisations.