integrate fsleyes to generate rendered images for defacing module

[raamana]

fsleyes render --scene 3d -rot 45 0 -30 --outfile tmp.99.result.deface.fsleyes.render_1.png tmp.99.result.deface.nii -dr 30 250 -cr 30 500 -in spline -bf 0.225 -r 100 -ns 500

thanks to Arshitha and Eric from NIH