Changes to fit new API for database transition.

Config files must implement the ConfigObject interface now instead of
DataObject. They no longer need to specify uniqueId.

pom.xml

@@ -36,7 +36,7 @@
 		<powermock.version>1.7.4</powermock.version>
 		<!-- More visible way how to change dependency versions -->
 		<spigot.version>1.13.2-R0.1-SNAPSHOT</spigot.version>
-		<bentobox.version>1.4.0</bentobox.version>
+		<bentobox.version>1.5.0-SNAPSHOT</bentobox.version>
 		<level.version>1.3.0</level.version>
 		<vault.version>68f14ec</vault.version>
 		<!-- Revision variable removes warning about dynamic version -->

src/main/java/world/bentobox/challenges/database/object/Challenge.java

@@ -311,7 +311,7 @@ public class Challenge implements DataObject
      */
     public ItemStack getIcon()
     {
-        return icon.clone();
+        return icon !=null ? icon.clone() : new ItemStack(Material.PAPER);
     }