removed checked in managedesent.dll and made it to use Nuget package.

this also moves managedesent.dll to a newer version that has a guard to an issue in esent.dll which time to time crash VS. (changeset 1397816)

src/Workspaces/Core/Portable/Workspace/Host/PersistentStorage/AbstractPersistentStorage.cs

@@ -48,18 +48,18 @@ public void Dispose()
         public void AddRefUnsafe()
         {
             Contract.Requires(refCounter >= 0);
-            refCounter++;
+            Interlocked.Increment(ref refCounter);
         }
 
         /// <summary>
         /// caller should make sure this is called in a thread-safe way
         /// </summary>
         public bool ReleaseRefUnsafe()
         {
-            refCounter--;
+            var changedValue = Interlocked.Decrement(ref refCounter);
 
-            Contract.Requires(refCounter >= 0);
-            return refCounter == 0;
+            Contract.Requires(changedValue >= 0);
+            return changedValue == 0;
         }
 
         public virtual void Close()