view libtests/0003/short-description @ 441:1a1ea05a94ce api-inversion

clarify audiodb_insert()

write audiodb_insert() (essentially to support the command-line client
audioDB::insert operation) in terms of audiodb_insert_datum() and a new
audiodb_insert_reference() function.  These two functions each do
exactly one thing and return failure if they're working on the wrong
kind of database.

1D insertion / point query using lib