Models: lots of small improvements, including:
added Recording.title field: store duplicated inherited titles for ordering in requests, store titles for pieceless recordings
added Recording.title_piece_object property to keep title in sync via custom save() method and display title in templates
added year and date fields, currently using DateField
cleanup
Templates for listing pieces and recordings: minor improvements, piece_header split into piece_music and piece_poetry, title code now uses Recording.title_piece_object property
Cleanup: obsolete template deleted