Rename all commandline db tools to consistently be named with the prefix "sgg-db-".
Update the sgg-db-admin-init usage text to be more accurate and fit better with the README Quick Start.
Rename "universe" to "galaxy" and create a galaxy table with referencial integrity for bodies.
Factor out some common deferred operations (possibly already standard in twisted?); fix a usage string; start organizing sgg-db-create-galaxy.