Implemented trapped chests & others

+ Added trapped chests
* Fixed a bunch of bugs in the redstone simulator concerning wires and
repeaters
* Other potential bugfixes

With thanks.
Normally you shouldn't be doing this - storing a `cBlockEntity` ptr for later. But this time it will work, because there's just no way a chunk with these chests would unload while a player has the chest open, because the player is too close to the chest.
In fact, that's why we can get away with storing the chest pointers in `cSlotAreaDoubleChest` down below.