Implement Syncback to support converting Roblox files to a Rojo project (#937)

This is a very large commit.
Consider checking the linked PR for more information.

rojo-test/syncback-tests/duplicate_rojo_id/input-project/container.model.json

@@ -0,0 +1,13 @@
+{
+  "className": "Folder",
+  "children": [
+    {
+      "name": "value_1",
+      "className": "ObjectValue"
+    },
+    {
+      "name": "value_2",
+      "className": "ObjectValue"
+    }
+  ]
+}

rojo-test/syncback-tests/duplicate_rojo_id/input-project/default.project.json

@@ -0,0 +1,11 @@
+{
+  "name": "duplicate_rojo_id",
+  "tree": {
+    "$className": "DataModel",
+    "ReplicatedStorage": {
+      "container": {
+        "$path": "container.model.json"
+      }
+    }
+  }
+}