Add "Backup Your Save" warning.

I keep breaking my saves when things go wrong. I don't want someone
losing a precious save file.
WIP: Fix item "age names", update name on use

The chainsaw "age name" (e.g. Chainsaw [108]) now updates when the
chainsaw is used (right now just by being equipped).

Chainsaws and petrol cans (gas cans) now seem to have properly
functioning ages and names.

Added a ton of debug print statements to track what's going on. The
debugger works, but I don't think it works in GNU/Linux as well as maybe
it does in Windows.

The chainsaw fill menu is getting closer but still needs to be debugged
some more.