Add a style options for map

The google map api has a style option that allows some flexibility. For instance you can have a grayscale map with this:

[ { stylers: [ { saturation: -100 } ] },{ featureType: "poi", stylers: [ { visibility: "simplified" } ] } ]

There is a wizard allowing to edit styles visually at http://gmaps-samples-v3.googlecode.com/svn/trunk/styledmaps/wizard/index... . When you have finished you styles, click on the "Show JSON" button, and copy the text (it should looks like the above example).

The following patch adds an option 'Map style (json)' at the admin/config/locationmap page. There, you can simply paste the example style above or your own.

google map api: https://developers.google.com/maps/documentation/javascript/styling?hl=f...