Add block material database

Taken from Bukkit's Material class, with credits.
Allows to know types and properties of blocks.
+ Use database for "is solid" checks
+ Add "can harm players" method
+ Faster movements, falling seems natural now
+ Shorter error message when ping failed

MinecraftClient/Mapping/World.cs

@@ -80,7 +80,7 @@ namespace MinecraftClient.Mapping
                 if (chunk != null)
                     return chunk.GetBlock(location);
             }
-            return Block.Air;
+            return new Block(Material.Air);
         }
 
         /// <summary>