Have a Bitbucket user on GitHub that can be granted read access so that we can import via SSH (BB-3743)

When importing a private git repository from a url such as this one:
git@github.com:Gunni/example.git
Bitbucket just fails saying there is no repository there, and also authenticating is done via a username/password if i use the https link, example:
https://Gunni@github.com/Gunni/example.git\\
You should create and use ssh keys for downloading/getting private repositories.