Hledger.Utils.Debug's "trace or log" functions are now controlled as
follows: to enable logging, append ",logging" to the program name at
startup (using withProgName). This also works when running in GHCI.
And they log to PROGNAME.log, not debug.log.
All (hopefully) debug logging in the hledger packages is now "trace or
log" capable.
This means that hledger-ui should now log all debug output to
./hledger-ui.log, with none of it appearing on the console.