Multiple display support

[lookeypl]

Engine should be able to render to multiple windows simultaneously. Features to implement:

• Displaying two independent windows within the same application on two different screens (see similar feature added to ex. GRID Autosport - secondary monitor displays TV-like live recap of what is happening during the race. Other use cases are additional help info on second screen, independent map display etc)
• Rendering extended to multiple displays at once - allows for increased FOV and more details shown. See how such situation is handled in ex. Battlefield 3.