Reduce file size of platform meshes

Now all platform meshes adhere to our policy of 1MB file size limits.

resources/definitions/hms434.def.json

@@ -46,7 +46,7 @@
             "6": "hms434_tool_7",
             "7": "hms434_tool_8"
         },
-        "platform":            "hms_platform.obj",
+        "platform":            "hms_platform.stl",
         "platform_offset":     [ 26, -13.2, 162.5],
         "platform_texture":    "hms434.png",
         "first_start_actions": ["MachineSettingsAction"],

resources/definitions/monoprice_ultimate.def.json

@@ -9,7 +9,7 @@
         "file_formats": "text/x-gcode",
         "icon": "wanhao-icon.png",
         "has_materials": true,
-        "platform": "wanhao_200_200_platform.obj",
+        "platform": "wanhao_200_200_platform.stl",
         "platform_texture": "Wanhaobackplate.png",
         "machine_extruder_trains": {
             "0": "wanhao_d6_extruder_0"

resources/definitions/stereotech_ste320.def.json

@@ -7,7 +7,7 @@
         "author": "Stereotech",
         "manufacturer": "Stereotech LLC.",
         "category": "Other",
-        "platform": "stereotech_ste320_platform.obj",
+        "platform": "stereotech_ste320_platform.stl",
         "platform_texture": "StereotechSte320backplate.png",
         "platform_offset": [
             0,

resources/definitions/ultimaker3.def.json

@@ -7,7 +7,7 @@
         "manufacturer": "Ultimaker B.V.",
         "visible": true,
         "file_formats": "application/gzip;text/x-gcode",
-        "platform": "ultimaker3_platform.obj",
+        "platform": "ultimaker3_platform.stl",
         "platform_texture": "Ultimaker3backplate.png",
         "platform_offset": [0, 0, 0],
         "has_machine_quality": true,

resources/definitions/ultimaker3_extended.def.json

@@ -8,7 +8,7 @@
         "quality_definition": "ultimaker3",
         "visible": true,
         "file_formats": "application/gzip;text/x-gcode",
-        "platform": "ultimaker3_platform.obj",
+        "platform": "ultimaker3_platform.stl",
         "platform_texture": "Ultimaker3Extendedbackplate.png",
         "platform_offset": [0, 0, 0],
         "has_machine_quality": true,

resources/definitions/ultimaker_s5.def.json

@@ -8,7 +8,7 @@
         "category": "Ultimaker",
         "visible": true,
         "file_formats": "application/x-ufp;text/x-gcode",
-        "platform": "ultimaker_s5_platform.obj",
+        "platform": "ultimaker_s5_platform.stl",
         "platform_texture": "UltimakerS5backplate.png",
         "platform_offset": [0, -30, -10],
         "has_machine_quality": true,

resources/definitions/wanhao_d4s.def.json

@@ -8,7 +8,7 @@
     "manufacturer": "Wanhao",
     "file_formats": "text/x-gcode",
     "has_materials": true,
-    "platform": "wanhao_225_145_platform.obj",
+    "platform": "wanhao_225_145_platform.stl",
     "platform_texture": "Wanhaobackplate.png",
     "machine_extruder_trains": {
         "0": "wanhao_d4s_extruder_0"

resources/definitions/wanhao_d6.def.json

@@ -8,7 +8,7 @@
     "manufacturer": "Wanhao",
     "file_formats": "text/x-gcode",
     "has_materials": true,
-    "platform": "wanhao_200_200_platform.obj",
+    "platform": "wanhao_200_200_platform.stl",
     "platform_texture": "Wanhaobackplate.png",
     "machine_extruder_trains": {
         "0": "wanhao_d6_extruder_0"

resources/definitions/wanhao_d6_plus.def.json

@@ -8,7 +8,7 @@
     "manufacturer": "Wanhao",
     "file_formats": "text/x-gcode",
     "has_materials": true,
-    "platform": "wanhao_200_200_platform.obj",
+    "platform": "wanhao_200_200_platform.stl",
     "platform_texture": "Wanhaobackplate.png",
     "machine_extruder_trains": {
         "0": "wanhao_d6_plus_extruder_0"

resources/definitions/wanhao_d9.def.json

@@ -7,7 +7,7 @@
         "manufacturer": "Wanhao",
         "file_formats": "text/x-gcode",
         "has_materials": true,
-        "platform": "wanhao_300_300_platform.obj",
+        "platform": "wanhao_300_300_platform.stl",
         "platform_texture": "Wanhaobackplate.png",
         "machine_extruder_trains": {
             "0": "wanhao_d9_extruder_0"