update OL3 to newer version

[sbsimo]

Currently we're using an old OL3 version (update end of 2014).
It would be good to include a newer version: from a quick check, some code adaptation is needed.

[sbsimo]

There's an issue with the popup and OpenLayers v3.12.1.
I suggest to update OL3 version after the work on the popup (issue #9 ).

[ireneITHACA]

Update: actual Openlayers version is the v3.11.0

[sbsimo]

newer ol versions don't support jquery for the creation of the Overlay object.
applied workaround by generating a DOM object with document.createElement instead of using jquery.