Added an utility to collect multiPointSources [skip CI]
Added an utility to collect multiPointSources [skip CI]


Former-commit-id: 7af10460c48cc822477940802a92349afb50c8c8 [formerly e5cd372f919d307ba5f2ffce6263da566906b72f]
Former-commit-id: 829eb628dcbd8e9205ea3c3ec5b2cb562669dce4
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine