Move nvidia docker environment variables to a user editable setting

[therishidesai]

nvdocker/nvdocker/nvdocker.py

Lines 7 to 9 in dd79257

	gpu_devices = ['/dev/nvidiactl', '/dev/nvidia-uvm', '/dev/nvidia1', '/dev/nvidia0']
	nvidia_driver = 'nvidia-docker'
	volumes = {'nvidia_driver_387.12':{'bind':'/usr/local/nvidia', 'mode':'ro'},

These were hardcoded in for the GPU cluster.

[narendasan]

arent these settings required to use the container with the module? Why would the user need to change these if trying to use nvdocker?