Urist's damage and health thing. (#10)

* Add prototype for temperature testing entity.

* Add Damageable, Destructible, Temperature. Add a prototype based on those.

* Works and cleaned up.

* Nerf

Content.Shared/GameObjects/PhysicalConstants.cs

@@ -0,0 +1,10 @@
+namespace Content.Shared.GameObjects
+{
+    /// <summary>
+    /// Contains physical constants used in calculations.
+    /// </summary>
+    class PhysicalConstants
+    {
+        public const float ZERO_CELCIUS = 273.15f;
+    }
+}