Fixed matches and candles not being able to burn papers. Also made Diona...

... join prompt appear for a bit longer.
This is successor to #6234.

**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 of cigs_lighters.dm