Add support for GitLab

[RichardJActon]

Adds support for gitlab personal access tokens and ssh setup

I created two new functions:

• set_gitlab_pat()
  • A copy of set_github_pat() with modifications to work with the gitlab API and the added instance parameter to allow you to set a gitlab instance other than gitlab.com (the default)
• ssh_setup_gitlab()
  • also a copy of ssh_setup_github() with the added instance param and modified for gitlab url forms