Initial bounding box as URL parameter

[nuest]

Add a URL parameter to configure the initial bounding box of the displayed map in lat lon coordinates. This would allow for smoother integration with other portals or catalogues, since the user will be shown a similar extend to the one she is looking at in the originating website. It also allows to drill down to a specific area, which is smaller than the full extend of all stations.

Example: http://sensorweb.demo.52north.org/jsClient/#map?extend=10.0,22.2,3.3,4.44 or http://sensorweb.demo.52north.org/jsClient/#map?extend=[40.712,-74.227],[40.774,-74.125]

Could be done with Leaflets fitBounds(..) > http://leafletjs.com/reference.html#map-set-methods

@janschulte Or would you do this by extending the permalink feature? I did not find documentation about the permalinks at http://52north.github.io/js-sensorweb-client/