Finds the FSLDIR from system environment or getOption("fsl.path")
for location of FSL functions
get.fsl(add_bin = TRUE)
get_fsl(add_bin = TRUE)Should bin be added to the fsl path?
All executables are assumed to be in FSLDIR/bin/. If not, and
add_bin = FALSE, they will be assumed to be in FSLDIR/.
NULL if FSL in path, or bash code for setting up FSL DIR
This will use Sys.getenv("FSLDIR") before getOption("fsl.path").
If the directory is not found for FSL in Sys.getenv("FSLDIR") and
getOption("fsl.path"), it will try the default directory /usr/local/fsl.