Allow the blobstore implementation to be configurable

[tom--pollard]

trafficstars

The blob library gocloud.dev/blob has various 'drivers' (for instance the gcsblob package) which makes it relatively easy to interact with different 'blobstore' type backends via a common api.

Utilising this extensibility to allow users to upload results to the supported (s3, azure etc) endpoints via a generic interface may make it easier for wider adoption.

[naveensrinivasan]

+1

[tom--pollard]

With #83 basic support was added for generic s3 endpoints for the results blobs. However, keeping this issue around for further expansion is probably worth while

[calebbrown]

Closing as this appears to be done (as per the docker-compose implementation)