0.4.9

• centred to primitive lattce transformation
• Niggli reduction and Buerger reduction for lattice basis
• added UnitCell::is_compatible_with_spacegroup()
• Topology-related improvements (Keitaro)
• functions SMat33::elements() and change_basis() were replaced – each was replaced with two new functions
• more options in gemmi-merge
• more Python bindings
• various fixes, in particular in validation in gemmi mtz2cif --depo.