[GNC] Access to Bugzilla + price handling in Transfer dialog

[Étienne Beaulé]

Hello! I'd like to get an account on your Bugzilla instance.

Also, I've recently made a PR to improve how currency conversion prices are
handled when using the Transfer dialog (such as when posting an invoice). I
think that when a price is inputted (rather than value), it should be saved
as a "user price" in the price database so that it gets used as the default
for future transfers on the same date. I think this would be a small thing
that'd make things easier for me.

Étienne