Sanitise InfoBubble Event Handling

[vicchi]

The default events trapped when a Marker with an infoBubble is instantiated are inconsistent across providers and need to be sanitised and made consistent.

For example, the Leaflet implementation sets a default click handler on the parent Marker to open the infoBubble when the Marker is clicked, whereas the Google v3 implementation sets a default click handler on the parent Marker only if the hover option is not set and instead sets a default onmouseover handler.