Throwing ammo cans while jetpacking

This needs to be added, but we're obviously a bit short on buttons.

1. I can add "use_jetpack" and "use_canister" commands, but those obviously only work if you use custom binds.

2. I can make it so the "saber attack style" button dispenses canisters, but that's kind of hacky and not really clean. You can have a lightsaber and ammo dispenser, etc

3. IMO the best solution, jetpack activates/deactivates with double jump, and +use operates normally. This is the most foolproof method, but it would require people to get used to pressing it.

I'd like to do both #1 and #3, please let me know if you have a better idea.