Bind effect removed if Spider moves or is killed.
Allow animated effects to be centered on a unit.
Allow effect actions to not have an attacker.

Spells will have an attacking unit, but unit traits might not.
Log the HP gained from a heal effect.
Animate spell casts and effects that cause damage.

Also added definition for new unit Druid that will cast spells (can't do
this yet).
Set up infrastructure to define spells.

First spell will be Lightning Bolt, cast by Druids.
X macros need convenient string uppercasing.
Hook up the ability for user to cast a spell.
Support animations with frames larger than one hex.

Lightning effect is the first user of this.  Druid spell cast now looks
good.
Made ranged attack into a trait.

You don't need to mention it in the unit config though.  We can figure it out
from the fields provided.
Anim for Lightning Bolt spell.
Allow the AI to cast spells.
Store spell damage in the action instead.

Instant effects that cause damage don't apply any change in status, so
they don't need to know about damage.
Bind effect needs to know attacking unit.

Otherwise we'll never unbind.