src/ulocollect: make it a Git submodule

.gitmodules

src/ulocollect

src/ulocollect/collecter.go

src/ulocollect/dummy_importer.go

src/ulocollect/file_system_collecter.go

src/ulocollect/go.mod

src/ulocollect/go.sum

src/ulocollect/importer.go

src/ulocollect/iri_fix_importer.go

src/ulocollect/iri_fix_importer_test.go

src/ulocollect/job_id.go

src/ulocollect/job_info.go

src/ulocollect/job_state.go

src/ulocollect/local_scheduler.go

src/ulocollect/package.go

src/ulocollect/scheduler.go

src/ulocollect/waiting_room.go