Support Github/Bitbucket/Gitlab in Desktop

[steve-winter]

I am unclear why we would not support the various repositories in Desktop mode, so proposing enabling.

Welcome feedback.

[jgadsden]

good point @steve-winter up to now it is because of the configuration needed for Github/Bitbucket/Gitlab, and working out how to do that for the desktop version

[steve-winter]

I am undecided if this or #828 is the appropriate outcome. I suspect #828 is the right outcome for desktop, but will have a think on both.