extend to 2/4 GPUs

[Happy2Git]

I have extended the GPU function to a multi-GPU version with a simple trick. Successfully tested on a 2-GPU machine and a 4-GPU machine.
The multi-GPU output on a 2-GPU machine is as follows:

CPU {cpu} {cputemp} | GPU {nvgpu} {nvgputemp} | Mem {mem} | SWAP {swap} | Net {netcomp}