Update ola.php

Now users can include an OpenStreetMap with a directive like the following:

(:ola-map
link=http://www.openstreetmap.org/?mlat=40.7300&mlon=-74.0054#map=16/40.7300/-74.0054:)

There is also a page variable $OSMLink containing the link from the directive which could be used like this:

(:ola-map
link=http://www.openstreetmap.org/?mlat=40.73001&mlon=-74.00541#map=16/40.7303/-74.0043:)

[[{$OSMLink}|View larger OpenStreetMap]]