Layer data is now processed layer by layer.

This is done to prevent the very large messages that would be sent otherwise.
Protobuf can't do anything with messages above 512MB. As we no longer send a
"collection" message, this should no longer occur.
CURA-1210

plugins/CuraEngineBackend/Cura.proto

@@ -2,14 +2,12 @@ syntax = "proto3";
 
 package cura.proto;
 
-
 message ObjectList
 {
     repeated Object objects = 1;
     repeated Setting settings = 2;
 }
 
-// typeid 1
 message Slice
 {
     repeated ObjectList object_lists = 1;
@@ -24,28 +22,13 @@ message Object
     repeated Setting settings = 5; // Setting override per object, overruling the global settings.
 }
 
-// typeid 3
 message Progress
 {
     float amount = 1;
 }
 
-// typeid 2
-message SlicedObjectList
-{
-    repeated SlicedObject objects = 1;
-}
-
-message SlicedObject
-{
-    int64 id = 1;
-
-    repeated Layer layers = 2;
-}
-
 message Layer {
     int32 id = 1;
-
     float height = 2;
     float thickness = 3;
 
@@ -70,20 +53,16 @@ message Polygon {
     float line_width = 3;
 }
 
-// typeid 4
 message GCodeLayer {
-    int64 id = 1;
     bytes data = 2;
 }
 
-// typeid 5
 message ObjectPrintTime {
     int64 id = 1;
     float time = 2;
     float material_amount = 3;
 }
 
-// typeid 6
 message SettingList {
     repeated Setting settings = 1;
 }
@@ -94,11 +73,9 @@ message Setting {
     bytes value = 2;
 }
 
-// typeid 7
 message GCodePrefix {
     bytes data = 2;
 }
 
-// typeid 8
 message SlicingFinished {
-}
+}