Removing/Adding from EntityCollection doesn't work with events suspended

In `KmlDataSource.js` when a `NetworkLink` is refreshed we remove old entities, then add new entities. We need to `resumeEvents()` then `suspendEvents()` in between the removes and adds or the entities don't update.

You can see the code here: https://github.com/AnalyticalGraphicsInc/cesium/pull/3538#discussion-diff-52938624R2420

I discovered this using the document https://github.com/tfili/geospatial-tools/blob/master/kmlServer/kml/nwl-interval.kml

This document refreshes a point's position by using a server that just moves a point every few seconds. The server can be found at https://github.com/tfili/geospatial-tools/tree/master/kmlServer.

Start in KmlDataSource.js at the NetworkLink refresh path and review the referenced pull-request discussion. Reproduce the issue with nwl-interval.kml and its moving-point server, then verify that refreshed entities update correctly when removals and additions occur while events are suspended.

Written by the indexing model from the issue text.