Code cleanup: includes into io-subfolders, compile-warnings

modules/gfx/tests/test_ent_pov_export.cc

modules/gui/src/data_viewer/data_viewer.cc

modules/gui/src/file_loader.hh

modules/gui/src/file_type_dialog.hh

modules/io/src/CMakeLists.txt

modules/io/src/mol/entity_io_sdf_handler.cc

modules/io/tests/test_exceptions.cc

modules/io/tests/test_io_crd.cc

modules/io/tests/test_io_dcd.cc

modules/io/tests/test_io_img.cc

modules/io/tests/test_io_pdb.cc

modules/io/tests/test_io_sdf.cc

modules/io/tests/test_mae_standalone.cc

modules/io/tests/test_mmcif_reader.cc

modules/io/tests/test_star_parser.cc