Compatibility with Piwigo 12

compatible with Piwigo 2.7

New languages:
* Norwegian (Norsk bokmål [NO]), thanks to paulen

Fix bug with PWG Stuffs block containing thumbnails

New languages:
* Slovak (Slovensky [SK]), thanks to dodo, xpace

technical changes
if you have any problem with the configuration, go to the config page, check your params and submit the form (anyway)

13 new languages

compatible with Piwigo 2.5

-multisize button is disabled for photos with a backside
-with Piwigo 2.4, backside won't appears at first load if not in the cache (just refresh the page)

- Fixed activation errors and when the plugin updated backside information .

solve prefilter issue which masks recto-verso properties on picture modify page

new parameter: mark pictures with a reverse on the thumbnails page
better integration of the button in the toolbar
use the new picture selector : less bugs

add Italiano, thanks to rio

New options :
- link position (top, bottom, toolbar)
- customisation of the link label

First public version