attribute access. New test for fileOrText decorator

Michiel Cottaar authored 6 years ago and Paul McCarthy committed 6 years ago

The functionality of merging multiple jobs is now ensured by allowing
for nested sequences of job-ids.

Also, a couple of FNIRT fixes - Jacobian option is an image and a couple of
options that were previously compulsary are now optional (because they are
not required in certain circumstances)