Added a test for duplicated tags
Fixed the number_of_ground_motion_fields
Merge pull request #1567 from gem/import-multiple-imts

Added a test for duplicated tags in import_gmf_scenario.py
Reflected the API change in hazardlib.calc.gmf.GmfComputer
Merge pull request #1568 from gem/gmfcomputer

Reflected the API change in hazardlib.calc.gmf.GmfComputer
Merge branch 'master' of github.com:gem/oq-engine into single-getter