Added oq plot_hmaps as a debugging tool [skip CI]
Added oq plot_hmaps as a debugging tool [skip CI]


Former-commit-id: 1daf4959d9499e591eb2c470da18e6560a03ca9b [formerly bbdb9f43bc3fdbaaeceb9919f44dfbce28e048c4]
Former-commit-id: 0e52ccad16e325676e4b6cc6a3a79fa59998a8d4
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine