DataMapper auto_migrate/auto_upgrade the default repository

tasks in question:
* rake dm:auto:migrate
* rake dm:auto:upgrade
Merge pull request #1298 from Ortuna/issue-1293

DataMapper auto_migrate/auto_upgrade the default repository
Merge remote-tracking branch 'upstream/master' into refresh-admin

* upstream/master:
  DataMapper auto_migrate/auto_upgrade the default repository