The Null Rod/Chaplain update

The original plan was to give the null rod some defensive properties against runes. Turns out I spent most of my time on other stuff. Playing chaplain should be a little more fun now.

* The null rod now protects from some runes and talismans in an AOE. (up to 1 tile away)
* Added a visual effect and sound for when the Null Rod's protection gets proc'd
* The null rod now deals double damage to constructs, shades and hell monsters.
* Supernatural creatures hit by the null rod will enter a "purged" state for 3 seconds:
* They cannot used any spell while purged.
* Their speed is divided by the number of seconds left before the purge ends.
* Getting hit again resets the 3 seconds counter
* Fixed a bug that caused mobs to become even faster if slowed while their base speed was negative
* Added visual indicators on the construct/shade HUD if you've been purged
* You can now store bibles on bookshelves HOLY SHIT WHY WASN'T THIS A THING YET?
* Ghosts now have a visual indicator on their HUD if they've been made visible (by an Arcane Tome for example)
* Using the Bible or Null rod on visible ghosts will make them invisible again.
* The chaplain's holy water flask may now be used on a mob, the ground or a wall to splash 5u of its content. (vampire hunters rejoice. of course the flask may be refilled with other reagents...)
* Tiles splashed with holy water become "holy", All of the chapel's tiles are holy by default.
* Visible ghosts cannot pass across holy turfs.
* visible ghosts cannot either teleport to people who are standing on an holy tile, or teleport to an area if all of this area's tiles are holy.
* The ghosts of cultists submit to the same limitations as visible ghosts.
* Holy tiles won't generate monster gateways or randomly transform into cult tiles once Nar-Sie has risen.(they'll still transform if Nar-Sie himself consumes them)
* Fixed a runtime error that caused human ghosts not to appear on sepia camera pictures.
* Ghosts and Animals appearing on pictures will now appear in their description as well.
* Ghosts now appear half-transparent on sepia pictures.
not to mention that the code about items that affect a ghost's visibility is actually in observer.dm. I removed that segment from ritual.dm in my latest commit.