Add damagetype enum and field to ProjectileEffectData
Add stat management to units
Start implementing fire effect.

Stat wear-off not high enough or not working (Forgot to set default values
probably)
Need to implement damage over time for fire.
Simplify UnitData Loading.

Spaceman, FoodCart, and Enemy now load their data using the generic
DataLoader.CollectData<T>.
This returns IEnumerable which must be cast appropriately.
(Single in case of Spaceman/FoodCart,
Dictionary<string, EnemyData> in case of Enemy)
Use CollectData to load WeaponData
Load SpriteData with DataLoader.CollectData
Use DataLoader.CollectData to load ParticleGeneratorData
Fix null array glitch in ProjectileEffect
Implement fire damage
Improve fire effect handling
Improve fire particle effect logic
Tweak flamethrower stats for balance
Add line segment geometry methods to XnaHelper
Re-implement StatusEffect as struct
Implement fire spread between units.

Possible issue:
With many units close together, fire may never go out.
Implement fire spread die-out.

A portion of the fire transferred from one unit to the other is lost, so
fires in groups eventually extinguish.

Needs some tweaking.
Add freeze-ray and cryo slow effect
Add cryo freeze effect
Add boomerang weapon
Implement projectile rotation