update changelog for 1.7.0 release (engine-1.7)
update changelog for 1.7.0 release (engine-1.7)


Former-commit-id: 278efc0bea258d7ca7a0444a32381b8dfe106b90
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine