first cut at new evolution machinery (no tests)
add tests, still missing tests for add_evolution_step
missed a file
switching computers
readd legacy registrations
Merge branch 'master' into feature.newevolve
add all packages to finished
coverage
use a btree as the finished step container, flesh out command-line script, commit when finished container first created to work around zodb root setdefault weirdness
remove legacy evolution code
fix todo after merging feature.newevolve branch; closes #64