Take advantage of upgraded Leaflet API

[JRInge]

If/when the main map page is upgraded to use Leaflet > v0.7, use map.eachLayer() to iterate layers instead of using a for ... in loop over the _layers property of the map.

[JRInge]

Use map.fitBounds() options in GME_displayPoints() to ensure that

• a) waypoints are not lost at the edges of the viewport (v0.6)
• b) map doesn't zoom in too far (v0.7)