Add more general item colouring system

This allows for other items, such as turtles, to be dyed in the future.
This also adds support for the ore dictionary, meaning you can use other
mod's dyes to colour items.

src/main/java/dan200/computercraft/shared/util/ColourUtils.java

@@ -0,0 +1,37 @@
+package dan200.computercraft.shared.util;
+
+import net.minecraft.item.ItemStack;
+import net.minecraftforge.oredict.OreDictionary;
+import org.apache.commons.lang3.ArrayUtils;
+
+public class ColourUtils
+{
+    private static final String[] DYES = new String[] {
+        "dyeBlack", "dyeRed", "dyeGreen", "dyeBrown",
+        "dyeBlue", "dyePurple", "dyeCyan", "dyeLightGray",
+        "dyeGray", "dyePink", "dyeLime", "dyeYellow",
+        "dyeLightBlue", "dyeMagenta", "dyeOrange", "dyeWhite"
+    };
+
+    private static int[] ids;
+
+    public static int getStackColour( ItemStack stack )
+    {
+        if( ids == null )
+        {
+            int ids[] = ColourUtils.ids = new int[ DYES.length ];
+            for( int i = 0; i < DYES.length; i++ )
+            {
+                ids[ i ] = OreDictionary.getOreID( DYES[ i ] );
+            }
+        }
+
+        for( int id : OreDictionary.getOreIDs( stack ) )
+        {
+            int index = ArrayUtils.indexOf( ids, id );
+            if( index >= 0 ) return index;
+        }
+
+        return -1;
+    }
+}