0.6.3

• new: normalization of amplitudes using so-called "Karle" approach, similar as in the CCP4 program ECALC
• added X-ray scattering coefficients for ions (previously, the charge of atom was ignored)
• pdb: reading CONECT records, and an option to also write them
• when reading pdb, if any chain has 2+ TER records, all TER records are ignored
• more configuration options for writing pdb files
• added functions Mtz::expand_to_p1() and Mtz::read_file_gz()
• cif::Block::find_value(tag) now returns also value from the corresponding loop if that loop has only one row
• changes in gemmi-validate related to validation with DDL2
• gemmi-sfcalc: added option --sigma-cutoff
• gemmi sf2map --mapmask: if the unit cells in coordinate file is different than in SF file, use only the latter
• improved transform_to_assembly(), expand_ncs() and rename_chain()
• cif2mtz: Mtz column for pdbx_DELPHWT has now label PHDELWT (#272)
• fixed ensure_asu(): phase-shift (for phases and H-L coefficients) was wrong
• fixed UnitCell::find_nearest_image() for non-crystals with NCS
• fixed DensityCalculator::requested_grid_spacing()
• changes and enhancements in add_chemcomp_to_block(), in solvent masking, in mtz2cif,
  and in several other places
• added python bindings to MtzToCif, cif::Ddl, PdbWriteOptions, changed how options for PDB writing are passed, more bindings for Mtz::Batch