sbig-snap: support all the device types
libsbig: add  sbig_strdev(), sbig_devstr()
sbig: parse config and set SBIG_DEVICE in environment
sbig-cooler: get SBIG_DEVICE from environment
sbig-cfw: read SBIG_DEVICE from environment
sbig-snap: get config file name from environment
sbig-info: get device from environment
sbig-snap: add some FIXMEs
doc: update config in README.md