Reuse the ssh key from github instead of asking user

[mscherer]

So, the current form is asking the user for its ssh key. It would be better to reuse the one from the user on github, since this can be downloaded.

For example, this url give mine:
https://github.com/mscherer.keys

[deepshikhaaa]

Yes. We can do this, but what if user has not uploaded their SSH key to github?

[mscherer]

I guess we could prefill the box with the key, and if the user want another one, then they would be able to change.

We could also fetch it from gerrit. And if a user has no ssh key on github nor gerrit, I am not sure how the said user would send patch or contribute, and therefor need a VM to debug anything :)