GPU2 PPD increase

With new revisions to the GPU2 core code, the GPU2 code is doing more science per ever in the same amount of time.  In the spirit of having the points equate to how much science is being done, we are going to increase the PPD of the GPU2 benchmark machine (ATI 3850 board — see the FAQ for details) to 1500 PPD.  We will revalue the most recent WU's (472X) and all future WU's will use this new PPD for benchmarking.