refactored LossMapXMLWriter
refactored LossMapXMLWriter


Former-commit-id: b2d0b8321cfbc6d7bd9cb61f08687708d073a9c8 [formerly 378b5336d8c61a3f16bd476aa6b08b13fb4a8cc5]
Former-commit-id: 4ffffee7474d170418f06614b1e8774cb9f22997
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine