Disable print sequence for all multi-extrusion machines

Also for ORD and whatever else we have. It is now more inherent in the setting and it gives a better indication of why the setting is disabled when you hover the 'i' in the setting visibility screen.

resources/definitions/fdmprinter.def.json

@@ -169,7 +169,7 @@
                 },
                 "machine_extruder_count":
                 {
-                    "label": "Number extruders",
+                    "label": "Number of Extruders",
                     "description": "Number of extruder trains. An extruder train is the combination of a feeder, bowden tube, and nozzle.",
                     "default_value": 1,
                     "minimum_value": "1",
@@ -3769,6 +3769,7 @@
                         "one_at_a_time": "One at a Time"
                     },
                     "default_value": "all_at_once",
+                    "enabled": "machine_extruder_count == 1",
                     "settable_per_mesh": false,
                     "settable_per_extruder": false,
                     "settable_per_meshgroup": false

resources/definitions/ultimaker3.def.json

@@ -71,8 +71,6 @@
         "prime_tower_position_x": { "default_value": 175 },
         "prime_tower_position_y": { "default_value": 179 },
 
-        "print_sequence": {"enabled": false},
-
         "acceleration_enabled": { "value": "True" },
         "acceleration_layer_0": { "value": "acceleration_topbottom" },
         "acceleration_prime_tower": { "value": "math.ceil(acceleration_print * 2000 / 4000)" },

resources/definitions/ultimaker_original_dual.def.json

@@ -72,9 +72,6 @@
         "machine_extruder_count": {
             "default_value": 2
         },
-        "print_sequence": {
-            "enabled": false
-        },
         "prime_tower_position_x": {
             "default_value": 185
         },