Fixes data type pre-value issues with MNTP, removes unecessary contentpicker.html and memberpicker.html overlays since treepicker.html is all that should be used, cleans up the treepicker one to be more inline with our current angular standards. Removes uneeded event handling from treepicker

src/Umbraco.Web/PropertyEditors/MultiNodePickerConfigurationTreeSource.cs

@@ -0,0 +1,20 @@
+using Newtonsoft.Json;
+
+namespace Umbraco.Web.PropertyEditors
+{
+    /// <summary>
+    /// Represents the 'startNode' value for the <see cref="MultiNodePickerConfiguration"/>
+    /// </summary>
+    [JsonObject]
+    public class MultiNodePickerConfigurationTreeSource
+    {
+        [JsonProperty("type")]
+        public string ObjectType {get;set;}
+
+        [JsonProperty("query")]
+        public string StartNodeQuery {get;set;}
+
+        [JsonProperty("id")]
+        public int? StartNodeId {get;set;}
+    }
+}