Adding user_mods.sh placeholder file. This file will be populates within each git branch, including the changes to the base image, the branch being specific to individual projects; modified the gitlab ci - now creates an image for each branch pushed to the remote, and named after the branch name.

Updating the startup script - changing location of user env var definitions to .bashrc, instead of .bash_profile

Updating the startup script - managing sym-links to expected persistent storage, Renvirons, and bashrc.

Adding a feature to move the home folder from the default /home/centos, to one provided by passing a HOME env var to the container.