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/BlockPalettes/BlockPalette.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace MinecraftClient.Mapping.BlockPalettes
+{
+    public abstract class BlockPalette
+    {
+        /// <summary>
+        /// Get mapping dictionary. Must be overriden with proper implementation.
+        /// </summary>
+        /// <returns>Palette dictionary</returns>
+        protected abstract Dictionary<int, Material> GetDict();
+
+        /// <summary>
+        /// Get material from block ID or block state ID
+        /// </summary>
+        /// <param name="id">Block ID (up to MC 1.12) or block state (MC 1.13+)</param>
+        /// <returns>Material corresponding to the specified ID</returns>
+        public Material FromId(int id)
+        {
+            Dictionary<int, Material> materials = GetDict();
+            if (materials.ContainsKey(id))
+                return materials[id];
+            return Material.Air;
+        }
+
+        /// <summary>
+        /// Returns TRUE if block ID uses old metadata encoding with ID and Meta inside one ushort
+        /// Only Palette112 should override this.
+        /// </summary>
+        public virtual bool IdHasMetadata
+        {
+            get
+            {
+                return false;
+            }
+        }
+    }
+}