Bunch of fixes for GH repo creation, should work fine now:

- _github_username => _github_login # better says what this actually is
- dont forget to run ssh-add on newly created ssh key so that we can push right away
- create the global git config constants in a way that allow us to use any number of gh users on one local account (also affects the ssh key naming)
 - add git remote in a way that user with system username != GH login can push