adapt source code for new containerization abilities

[lundq163]

current test version of container lives here: /home/faird/shared/code/internal/GUIs/seg-model-creation-gui/seg-model-creation-gui_Gui_docker_TM.sif

[lundq163]

We can utilize fakeroot option with overlay to write out intermediate files to a separate overlayed directory. This will be helpful when troubleshooting the next steps (see sub-issues). For now, this can be used to temporarily execute the containerized GUI after making an overlay dir for intermediate files:
singularity run --cleanenv --env="DISPLAY=$DISPLAY" --fakeroot --overlay ./overlay /home/faird/shared/code/internal/GUIs/seg-model-creation-gui/seg-model-creation-gui_Gui_docker_TM.sif