enhance preferences to select which graphics card to use for 3d testing

[Al Edlund]

when there are multiple graphics cards available, select which one will be used for 3d testing. Multiple graphics cards from different vendors is becoming more common on newer systems and default selecting the native processor chip may not lead to a solution set of numbers that accurately reflect what is happening to performance.

[Tim (PassMark)]

In most cases it isn't possible for PerformanceTest to choose the graphics card to run on (particularly the older DX9/10/11 tests) and this is determined by the device drivers as the application is launched. This is why the graphics card must be selected before PerformanceTest is run, eg such as selecting the high performance option on Nvidia based systems.