Added --version-db
Added --what-if-I-upgrade functionality
Merge branch 'master' of github.com:gem/oq-engine into what-if-I-upgrade
Listing the safe scripts too
Fixed the listing of the safe scripts
Added a bit more of explanation
Ask for confirmation before upgrading
Do not ask for confirmation if there is nothing to do
Fixed a bug with --yes
Merge pull request #1517 from gem/what-if-I-upgrade

--what-if-I-upgrade functionality