Feature Request: Allow users to add orgs to Metecho without creating them.

[codefriar]

As a user of Metecho with a moderately complex org I need a faster way to create scratch orgs for work. It currently takes ~60-80 minutes for one of our scratch orgs to be spun up and ready for development. This is almost entirely time spent installing managed packages. This becomes an impediment when the work being done only takes 45 minutes (say, adding a flow). Our solution, here at Chief, is to utilize scratch org pooling. Our CI system maintains a pool of 15 pre-created scratch orgs with all our managed packages pre-installed. Our developers and Admins can 'adopt' a scratch org from the pool and are given the user/pass when they adopt it. If Metecho allowed us to add an org without having to create the scratch org, this would allow us to use our pool'd orgs. It would also allow users to authorize source-tracking enabled sandboxes for use in Metecho.