replace Dunbrack lib by our own backbone dependent rotamer libary

doc/tests/scripts/sidechain_steps.py

extras/data_generation/rotamer_library/README

...as/data_generation/rotamer_library/concatenate_library.sh

...amer_library/cullpdb_pc40_res1.6_R0.25_d180913_chains5877

extras/data_generation/rotamer_library/do_bbdep_lib.py

extras/data_generation/rotamer_library/fetch_data.py

.../data_generation/rotamer_library/rotamer_lib_creation.cmd

modelling/doc/sidechain_reconstruction.rst

modelling/pymod/_pipeline.py

modelling/pymod/_reconstruct_sidechains.py

modelling/src/sidechain_env_listener.cc

modelling/tests/test_sidechain_reconstruction.py

sidechain/data/CMakeLists.txt

sidechain/data/portable_bb_dep_lib.dat

sidechain/doc/loading.rst

sidechain/pymod/export_sidechain_object_loader.cc

sidechain/src/sidechain_object_loader.cc

sidechain/src/sidechain_object_loader.hh

sidechain/tests/test_rotamers.cc