prevent leaking disks by persisting on first delete attempt
launch plugin registration worker via worker_launcher
cleaning up some server code. No functional changes.
rename to disks per PR
update description in default config.
Merge pull request #497 from continuuity/feature/server-cleanup

cleaning up some server code. No functional changes.
Merge pull request #495 from continuuity/feature/google-delete-retry-fix

prevent leaking disks by persisting on first delete attempt
Merge pull request #498 from continuuity/feature/plugin-registration-launcher

launch plugin registration worker via worker_launcher