Fixes for cctools_gpu_autodetect.

Renamed gpu_autodetect to cctools_gpu_autodetect.

Redirected error messages to stderr.

Fixed bashisims.
Removed gpu_info_get debug message.
Merge pull request #323 from btovar/rampantmonkey-gpu_autodetection

Rampantmonkey gpu autodetection
Wrap nvidia-smi (a binary for managing NVIDIA gpus which is shipped with the linux driver) to determine the number of GPUs available.

Incorporated automatic detection in work_queue_worker.
Mirror link API names.
reduce variable scope
d_namlen is Darwin specific
Add path_lookup for e.g. $PATH exe lookups.

* pull-316:
  d_namlen is Darwin specific
  reduce variable scope
  generalize to any search string.
  prepend cwd unless test string is an absolute path
  lookup executable in search path
write dax to file instead of stdout
create replica catalog for all input files
create transform catalog for dax export
example usage instructions to plan DAX version of workflow
more verbose path_lookup function