Support update on pan for FeatureLayer

[peterneubauer]

When panning, new data in the feature layer, edited from other sources, should show up in the layer, much like in the native ESRI webviewer.

[patrickarlt]

@peterneubauer it should pick up edits/additions if you pan far enough. But we can't figure out if a feature was deleted on the service and remove it from the map without a significant amount of work.

The alternative could be to keep an eye on #665 and then wrap layer.refresh() in a setTimeout

[jwasilgeo]

Closing due to inactivity. Feel free to reopen and discuss again if you'd like.