New Admin users for GitHub and Bitucket and Bintray

[Martijn Verburg]

Hi all,

I've set-up some adoptopenjdk-admin users for both BitBucket and GitHub
which can serve as the accounts for any build servers, CI, Devops etc.

I'm uploading the latest VirtualBox image to Bintray as well, once that's
done we'll try to get the openjdk virtual images team together again and
try to finish off that developer VM work.

Cheers,
Martijn