Moved machine_nozzle_size from machine_settings to categories/resolution so it is exposed in the UI.

Cherry pick from master.
Conflicts:
	resources/machines/ultimaker2.json
	resources/machines/ultimaker_original.json

Contributes to issue CURA-276.

resources/machines/fdmprinter.json

@@ -57,9 +57,6 @@
             "description": "Number of extruder trains. An extruder train is the combination of a feeder, bowden tube, and nozzle.",
             "default": 1
         },
-        "machine_nozzle_size": { 
-            "description": "The inner diameter of the hole in the nozzle.",
-            "default": 0.4, "SEE_machine_extruder_trains": true },
         "machine_nozzle_tip_outer_diameter": { 
             "description": "The outer diameter of the tip of the nozzle.",
             "default": 1, "SEE_machine_extruder_trains": true  },
@@ -150,6 +147,15 @@
             "visible": true,
             "icon": "category_layer_height",
             "settings": {
+                "machine_nozzle_size": {
+                    "label": "Nozzle Diameter",
+                    "description": "The inner diameter of the hole in the nozzle.",
+                    "unit": "mm",
+                    "type": "float",
+                    "default": 0.4,
+                    "min_value": "0.001",
+                    "visible": false
+                },
                 "layer_height": {
                     "label": "Layer Height",
                     "description": "The height of each layer, in mm. Normal quality prints are 0.1mm, high quality is 0.06mm. You can go up to 0.25mm with an Ultimaker for very fast prints at low quality. For most purposes, layer heights between 0.1 and 0.2mm give a good tradeoff of speed and surface finish.",

resources/machines/ultimaker2.json

@@ -13,9 +13,6 @@
     
     "machine_extruder_trains": [
         {
-            "machine_nozzle_size": {
-                "default": 0.4
-            },
             "machine_nozzle_heat_up_speed": { 
                 "default": 2.0 
             },
@@ -66,7 +63,7 @@
             ]
         },
         "machine_center_is_zero": { "default": false },
-        "machine_nozzle_size": { "default": 0.4 },
+        "machine_nozzle_size": { "default": 0.4, "description": "The inner diameter of the hole in the nozzle. If you are using an Olsson Block with a non-standard nozzle then set this field to the nozzle size you are using." },
         "machine_nozzle_heat_up_speed": { "default": 2.0 },
         "machine_nozzle_cool_down_speed": { "default": 2.0 },
         "gantry_height": { "default": 55 },

resources/machines/ultimaker_original.json

@@ -18,9 +18,6 @@
 
     "machine_extruder_trains": [
         {
-            "machine_nozzle_size": {
-                "default": 0.4
-            },
             "machine_nozzle_heat_up_speed": { 
                 "default": 2.0 
             },