Added help to the tool, use "oqrev --help" to get it.
Added help to the tool, use "oqrev --help" to get it.


Former-commit-id: 1df37a21a72a47c97da58bbfdb2499d49ff6d5f1
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine