update Printrbot Simple definition

* Add platform mesh
* Default nozzle size is 0.4mm
* Updated start gcode to correct bed origin after auto-level

resources/definitions/printrbot_simple.def.json

@@ -8,6 +8,7 @@
         "author": "Calvindog717",
         "manufacturer": "PrintrBot",
         "category": "Other",
+        "platform": "printrbot_simple_metal_platform.stl",
         "file_formats": "text/x-gcode"
     },
 
@@ -17,7 +18,7 @@
         "machine_height": { "default_value": 150 },
         "machine_depth": { "default_value": 140 },
         "machine_center_is_zero": { "default_value": false },
-        "machine_nozzle_size": { "default_value": 0.3 },
+        "machine_nozzle_size": { "default_value": 0.4 },
         "material_diameter": { "default_value": 1.75 },
         "machine_nozzle_heat_up_speed": { "default_value": 2 },
         "machine_nozzle_cool_down_speed": { "default_value": 2 },
@@ -33,10 +34,10 @@
         "machine_gcode_flavor": { "default_value": "RepRap (Marlin/Sprinter)" },
 
         "machine_start_gcode": {
-            "default_value": "G21 ;metric values\nG90 ;absolute positioning\nM82 ;set extruder to absolute mode\nM107 ;start with the fan off\nG28 X0 Y0 ;move X/Y to min endstops\nG28 Z0 ;move Z to min endstops\nG29 ; auto bed-levelling\nG1 Z15.0 F9000 ;move the platform down 15mm\nG92 E0 ;zero the extruded length\nG1 F200 E3 ;extrude 3mm of feed stock\nG92 E0 ;zero the extruded length again\nG1 F9000\n;Put printing message on LCD screen\nM117 Printing..."
+            "default_value": "G21       ;metric values\nG90       ;absolute positioning\nM82       ;set extruder to absolute mode\nM107      ;start with the fan off\nG28 X0 Y0 ;home X/Y\nG28 Z0    ;home Z\nG92 E0    ;zero the extruded length\nG29       ;initiate auto bed leveling sequence\nG92 X132.4 Y20 ;correct bed origin (G29 changes it)"
         },
         "machine_end_gcode": {
-            "default_value": "M104 S0 ;extruder heater off\nM140 S0 ;heated bed heater off (if you have it)\nG91 ;relative positioning\nG1 E-1 F300  ;retract the filament a bit before lifting the nozzle, to release some of the pressure\nG1 Z+0.5 E-5 X-20 Y-20 F9000 ;move Z up a bit and retract filament even more\nG28 X0 Y0 ;move X/Y to min endstops, so the head is out of the way\nM84 ;steppers off\nG90 ;absolute positioning"
+            "default_value": "M104 S0     ;extruder heater off\nM140 S0     ;heated bed heater off (if you have it)\nM106 S0     ;fan off\nG91         ;relative positioning\nG1 E-1 F300 ;retract the filament a bit\nG1 Z+1 E-5 F9000 ;move Z up a bit and retract even more\nG28 X0 Y0   ;home X/Y, so the head is out of the way\nM84         ;steppers off\nG90         ;absolute positioning"
         }
     }
 }