Some improvements to flamethrowers

- Cumbersome menu has been removed
- Clicking on a fully set flamethrower will set ignition
- Using a crowbar on it will remove the plasma tank if any if the
flamethrower is unlit (for obvious reasons)
- Flamethrower now uses tank output pressure as a basis, might still be
buggy

This is kinda lackluster compared to the overhaul I wanted to make
(flamethrowers still spew a custom fuel instead of actual plasma), but I
simply can't seem to unfuck the code properly
Merge pull request #1196 from dylanstrategie/Flamethrower

Some improvements to flamethrowers