Delete items in nested dictionary based on value.

[Brian L. Troutwine]

This is a general reply to all.

Thanks for all the suggestions. I hadn't really thought about filtering
empty dictionaries because the data I'm processing won't have them, but
it does make for a much nicer, more general filter. I did end up using
bearophileH's code, but that's mostly because he got there first. Each
solution functioned as advertised.

Again, thanks for all the help.