Merge of extensible_properties branch

The idea behind this work was to be able to fetch any attribute using member properties.

It also includes french translation and a few fixes.

The only thing which could be an issue is the deletion of "description='bio'" from the properties_map. As stated in the file, it can be RichText and thus break the module.

So I think we should talk about it before merging this pull request. I think a solution would be to rename the bio attribute to description and add description as a default element of the whitelist. It is not the best solution as it would break implementation directly using the bio attribute of the member content though.