add song numbers corresponding to song book

[ConcernedHobbit]

add song numbers from the 2015 physical song book so searching is easier

• displayed before song name
• songs can be searched using numbers
• search prioritizes song numbers when typing just numbers
• song numbers can be toggled off (see futureproofign idea below)

futureproofing: add generic "songbook-number" list attribute so multiple years can be switched between in ui, e.g. none, 2015 and 2022/2023, and it will update the song numbers in the ui for the current session

[ConcernedHobbit]

closed by bbacaae195f2fb9f28e7158c1308a9df468d9297