Various bugfixes

Averice/Avarice

code in mondata.c was preventing MR_DRAIN and MR_SICK from having an effect

code in explode.c was preventing the various elemental explosions from working properly

a mistake in Mother Lilith's entry was preventing her from using her artifact weapon in combat.

a mistake in dobinding was leading to nullpointers.
New encyclopedia entries and gehennom named monster tweaks
Dungeon Ferns

Porting dungeon ferns over from UnNetHack.

Creating new "Plant" ('#') monster class for them.
Merge branch 'master' of https://github.com/Chris-plus-alphanumericgibberish/dnethack.git