Git identity

[PIG208]

Users cannot commit directly in an IDE session without setting their information every time. Originally the plan was to utilize GIT_COMMITTER_NAME and GIT_COMMITTER_EMAIL environment variables so that git commit works out of the box. But the IDE UI does not support that. So this instead only passes the environment variable to theia-init which generates .gitconfig for the user.

This has been lightly tested in a minikube environment. It is confirmed to be working with both the Theia UI and git CLI.

TODOs:

• We might want to use the email provided by GitHub because the netid email does not necessarily link to the user.
• To make customization available for the users, we need to update the UI (perhaps the profile tab).
• To make things further customizable, we might implement a feature to allow students to customize their dot files. This PR is only a minimally workable solution to allowing the user to use git commit right away.