Fix showing material options for 3rd party printers

CURA-2287

resources/definitions/fdmprinter.def.json

@@ -10,6 +10,7 @@
         "manufacturer": "Ultimaker",
         "file_formats": "text/x-gcode;application/x-stl-ascii;application/x-stl-binary;application/x-wavefront-obj;application/x3g",
         "visible": false,
+        "has_materials": true,
         "preferred_material": "*generic_pla*",
         "preferred_quality": "*normal*",
         "machine_extruder_trains":

resources/definitions/ultimaker2.def.json

@@ -14,6 +14,7 @@
         "platform": "ultimaker2_platform.obj",
         "platform_texture": "Ultimaker2backplate.png",
         "platform_offset": [9, 0, 0],
+        "has_materials": false,
         "supported_actions":["UpgradeFirmware"]
     },
     "overrides": {