Rename asset_id -> asset_ref
Rename asset_id -> asset_ref


Former-commit-id: 1ca92b4f31aa09aefd77ed48a0f4d35715c9608f [formerly 7f31e3c0876932a4f327f1fb003cb5d953e0a8c6]
Former-commit-id: 94f8ac765df3fc949e7c1e97ac90b8be7067ae0e
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine