Rods, new magic items

Rods are a new type of magic item that share several characteristics.

* All rods begin with zero charges, and lose their charges if they
change hands.

* Rods gain a charge whenever their owner kills a monster, or whenever
the owner visits a safe place.

* Rods are wands that only work on their owner, and thus do not require
targeting. Pressing space or double-clicking one will use their
abilities immediately.

* A player may only carry five rods at any one time.

* Rods' descriptions will show how many charges they have, how many they
consume per use, and how many they can hold total. For instance, Gnarled
Staves consume one charge per use and can only hold three charges, while
a rod of armor of Gort consumes 20 charges per use and can hold 20
charges.

The design behind these items is to give players interesting gear
choices. Heal wands, vamp wands, and gnarled staves have been
significantly upgraded and converted into rods. In addition, four
critical buffs have been implemented as spell rods: bless, super
strength, detect invisible, and armor of Gort. These spell rods cannot
be recharged by visiting an inn; thus they can only be recharged by
killing monsters, granting builders the ability to employ critical buffs
at a moderate spellpower and without burning reagents.

Of course, heal wands are the baseline rod. Choosing to carry a rod of
armor of Gort means you are carrying one less heal wand. Heal wands have
had their variance reduced, but their average heal amount is still 6.
Five charges per heal wand means 30 health per wand average; five heal
wands total means a player can hold 150 health in reserve with heal
wands. Each specialty wand is therefore a choice made over having
roughly 30 more health. Is it worth it to build with armor of Gort?
Probably. Is it worth it to build with Detect Invisible? Maybe...

In addition, this should help significantly with player downtimes
between monsters.