Make circle.yml fork-friendly

[murphyke]

The main change is the introduction of USER_NAME (CIRCLE_PROJECT_USERNAME) to avoid using the original repo's github organization in URLs.

Other minor changes:

• dms runs with more verbose logging.
• Errors when starting dms or dmsa are caught directly.
• Gross failures of dms and dmsa containers are caught directly.
• If dms or dmsa do not respond, the container logs are dumped.
• dms and dmsa logs are saved as artifacts.

For PRs of forks to be tested, CircleCI advanced settings need to be set:

• "Build forked pull requests" => "On"
• "Pass secrets to builds from forked pull requests" => "Off"

The latter may have no effect right now, but it seems needed for safety.

[bruth]

LTGM

[bruth]

@aaron0browne Any qualms with this?