added entity io handler for mmcif format

modules/io/src/CMakeLists.txt

modules/io/src/io_manager.cc

modules/io/src/mol/CMakeLists.txt

modules/io/src/mol/entity_io_mmcif_handler.cc

modules/io/src/mol/entity_io_mmcif_handler.hh

modules/io/src/mol/star_parser.cc