add support for user chord set hierarchies in support of the following use case of a huge chord pack:
gig books
book 1
song 1
...
song 999
...
book 999
song 1
...
song 999
this would allow a single pack download with large numbers of books with large numbers of songs – even subcategorized by genre, etc. of arbitrary hierarchy depth while still supporting reasonable navigational (scaler ui) and chord management (chord author) experiences…