Default backbone scoring is now setup whenever needed (lazy initialization).

doc/tests/scripts/modelling_close_small_deletions.py

doc/tests/scripts/modelling_fill_loops_by_database.py

doc/tests/scripts/modelling_fill_loops_by_monte_carlo.py

doc/tests/scripts/modelling_model_termini.py

modelling/doc/pipeline.rst

modelling/pymod/_closegaps.py

modelling/pymod/_mtm.py

modelling/pymod/_pipeline.py

modelling/pymod/export_model.cc

modelling/src/model.cc

modelling/src/model.hh

modelling/tests/test_close_gaps.py

modelling/tests/test_pipeline.py