Made lighters, matches, and candles subtypes of the new /obj/item/weapon/flame (for stuff which can burn paper and things), also made Diona prompt last a bit longer

**Changes:**
* The prompt which pops up when someone's harvesting a Diona pod lasts a bit longer (20 seconds instead of 7.5) so players don't miss it and have to wait for a whole 'nother growth before they can join as a nymph.
* Matches and candles can now burn papers, just like lighters do.
  * This was done by making match, candle, and lighter part of /obj/item/weapon/flame. Flame's only functional characteristic is that it has the lit var, for now, but that could change with some cleanup.

This is probably a dumb amount of changes for the effect, but it's mostly renaming, and I figured this would be better in the long run instead of doing special checks for anything which can be lit on fire (which were already in place).

Also, bc556b7's message is incorrect, I'm just too lazy to change it. It says /obj/item/flame, when it's actually /obj/item/weapon/flame, as said above.