Hardware coloring for itemstacks

Adds the possibility to colorize item stacks based on their metadata.

In the item/node definition you can specify palette (an image file)
and color (fallback color if the item has no palette or metadata).
Then you can add palette_index to the metadata.

Dropped itemstacks with different colors do not merge.

src/script/common/c_content.h

@@ -89,7 +89,8 @@ void               push_tool_capabilities    (lua_State *L,
 ItemDefinition     read_item_definition      (lua_State *L, int index,
                                               ItemDefinition default_def);
 void               read_object_properties    (lua_State *L, int index,
-                                              ObjectProperties *prop);
+                                              ObjectProperties *prop,
+                                              IItemDefManager *idef);
 void               push_object_properties    (lua_State *L,
                                               ObjectProperties *prop);