Options by zoom strategy example

Shows the use of the OptionsByZoom strategy.

The current example demonstrate a single Vector layer using multiple data sources changing the featureType option of the protocol (WFS-T here) and format (GML here) so that each zoom level loads with different data.

Because this layer doesn't have different data sources, a fictive featureType value is given for zoom levels 4, 5 and 7 to show the options changes and that features from other levels get destroyed. The map starts at zoom level 6.