revert RangeIndexManager to internal in Storewrapper

Author: vazois

libs/server/StoreWrapper.cs

@@ -121,7 +121,7 @@ public sealed class StoreWrapper
         /// <summary>
         /// RangeIndex (BfTree) manager shared across sessions
         /// </summary>
-        public readonly RangeIndexManager rangeIndexManager;
+        internal readonly RangeIndexManager rangeIndexManager;
 
         /// <summary>
         /// Definition for delegate creating a new logical database