Split AssFile into separate lists for each section

aegisub/src/ass_file.cpp

aegisub/src/ass_file.h

aegisub/src/ass_karaoke.cpp

aegisub/src/ass_parser.cpp

aegisub/src/ass_parser.h

aegisub/src/audio_timing_dialogue.cpp

aegisub/src/auto4_lua.cpp

aegisub/src/auto4_lua.h

aegisub/src/auto4_lua_assfile.cpp

aegisub/src/base_grid.cpp

aegisub/src/command/edit.cpp

aegisub/src/command/grid.cpp

aegisub/src/command/subtitle.cpp

aegisub/src/command/time.cpp

aegisub/src/dialog_attachments.cpp

aegisub/src/dialog_kara_timing_copy.cpp

aegisub/src/dialog_selection.cpp

aegisub/src/dialog_shift_times.cpp

aegisub/src/dialog_spellchecker.cpp

aegisub/src/dialog_style_editor.cpp