Min & max values for extruder prime pos are now enforced for Ultimaker machines

CURA-2375

resources/definitions/ultimaker.def.json

@@ -20,6 +20,16 @@
         },
         "material_standby_temperature": {
             "minimum_value": "0"
+        },
+        "extruder_prime_pos_y":
+        {
+            "minimum_value": "0",
+            "maximum_value": "machine_depth"
+        },
+        "extruder_prime_pos_x":
+        {
+            "minimum_value": "0",
+            "maximum_value": "machine_width"
         }
     }
 }