* Allow width, height and maxZoom to be specified
* Add images to city marker tiddlers
* Initial support for custom popups
* Custom popup templates for the US and Canadian example data
* Popups should use the geomap as their parent widget
This lets root widget messages work
* Typo in default popup template
* Clean up the use of popup templates
* Allow GeoJSON features to be hidden via a checkbox
* Popup template for volcano dataset
* Add Natural Earth country data
* Optimise marker SVG
