expose what IStructureDefinition this constructable is using

src/main/java/com/gtnewhorizon/structurelib/alignment/constructable/IConstructable.java

@@ -1,5 +1,6 @@
 package com.gtnewhorizon.structurelib.alignment.constructable;
 
+import com.gtnewhorizon.structurelib.structure.IStructureDefinition;
 import cpw.mods.fml.relauncher.Side;
 import cpw.mods.fml.relauncher.SideOnly;
 import net.minecraft.item.ItemStack;
@@ -10,6 +11,13 @@ import net.minecraft.item.ItemStack;
 public interface IConstructable {
     void construct(ItemStack stackSize, boolean hintsOnly);
 
+    /**
+     * Get the structure definition used for this constructable. Can be null if this constructable is not backed by one.
+     */
+    default IStructureDefinition<?> getStructureDefinition() {
+        return null;
+    }
+
     @SideOnly(Side.CLIENT)
     String[] getStructureDescription(ItemStack stackSize);
 }

src/main/java/com/gtnewhorizon/structurelib/alignment/constructable/ISurvivalConstructable.java

@@ -3,6 +3,7 @@ package com.gtnewhorizon.structurelib.alignment.constructable;
 import com.gtnewhorizon.structurelib.alignment.enumerable.ExtendedFacing;
 import com.gtnewhorizon.structurelib.structure.AutoPlaceEnvironment;
 import com.gtnewhorizon.structurelib.structure.IItemSource;
+import com.gtnewhorizon.structurelib.structure.IStructureDefinition;
 import com.gtnewhorizon.structurelib.structure.ISurvivalBuildEnvironment;
 import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.entity.player.EntityPlayerMP;