Implement entity types (#1001)

Implement palette generation and investigate palette changes between
versions. Turns out 1.13- has legacy IDs, 1.14 switches to entity
palette and 1.15 refreshes the whole palette just to insert Bee.

Also refactor entity handling code here and there.

MinecraftClient/Mapping/EntityPalettes/EntityPalette.cs

@@ -0,0 +1,51 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace MinecraftClient.Mapping.EntityPalettes
+{
+    public abstract class EntityPalette
+    {
+        /// <summary>
+        /// Get mapping dictionary. Must be overriden with proper implementation.
+        /// </summary>
+        /// <returns>Palette dictionary</returns>
+        protected abstract Dictionary<int, EntityType> GetDict();
+
+        /// <summary>
+        /// Get mapping dictionary for pre-1.13. May be overriden with proper implementation.
+        /// </summary>
+        /// <returns>Palette dictionary for non-living entities (pre-1.13)</returns>
+        protected virtual Dictionary<int, EntityType> GetDictNonLiving()
+        {
+            return null;
+        }
+
+        /// <summary>
+        /// Get entity type from type ID
+        /// </summary>
+        /// <param name="id">Entity type ID</param>
+        /// <returns>EntityType corresponding to the specified ID</returns>
+        public EntityType FromId(int id, bool living)
+        {
+            Dictionary<int, EntityType> entityTypes = GetDict();
+            Dictionary<int, EntityType> entityTypesNonLiving = GetDictNonLiving();
+
+            if (entityTypesNonLiving != null && !living)
+            {
+                //Pre-1.13 non-living entities have a different set of IDs (entityTypesNonLiving != null)
+                if (entityTypesNonLiving.ContainsKey(id))
+                    return entityTypesNonLiving[id];
+            }
+            else
+            {
+                //Post-1.13 entities have the same set of IDs regardless of living status
+                if (entityTypes.ContainsKey(id))
+                    return entityTypes[id];
+            }
+
+            throw new System.IO.InvalidDataException("Unknown Entity ID " + id + ". Is Entity Palette up to date for this Minecraft version?");
+        }
+    }
+}