utils/config:
utils/config:

Added capability for the user to set a "OQ_CONFIG_FILE" envvar, to specify
a custom config file to override defaults.


Former-commit-id: 9f4029a7c4e560b36d7354b571961848ad7abbd8
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine