Map tips show up in the wrong location

[chrisclaydon]

1. Specify a tooltip and/or URL in an MG layer.

2. Add the layer to a map and the map to a Fusion layout.

3. View the FWL and hover the cursor over a feature.

RESULT: The Tooltip/URL appears far, far to the left of the cursor.

Expected: The tooltip should display right beside the cursor.

[madair]

(In [1644]) closes #156: add mapDiv offset to the tip position