Allow file paths as input to calwf3

[cshanahan1]

It would be useful for other functions that call calwf3 (or that run it on organized data) to be able to input file paths, rather than needing to change directories in a script because it only allows file names.

[cshanahan1]

Note on this, you can give it a path, but that path is limited to 6 additional characters including slashes..

calwf3.e data/input_file.fits works
calwf3.e a/b/c/input_file.fits works

calwf3 dataaa/input_file.fits does not work
calwf3 a/b/c/d/input_file.fits does not work

@mdlpstsci should I make an issue in hstcal for this?