Ability to set/change an extent to the graticule and to change the interval

[shane-brennan]

Hi,

I added the ability to pass in/change an extent (such as the current map.getBounds()). This allows small intervals with very good performance when zoomed in. I also added the ability to change the interval. Changes to extents and intervals are set via a refresh() function. I created a demo to show the interval and extent changing as the user pans/zooms the map. Critiques are welcome, for example, the added extent functionality doesn't work so well with the Mollweide projection due to it's strange handling of map.getBounds() (when zoomed out, map.getBounds().getWest() and ...getEast() return 0)

[bhaskarvk]

+1