Allow data sourcing from an external provider in a template

[MrGecko]

Related to: Capitains/MyCapytain#159

In order to be able to enrich some data on the rendered page (like adding some typographical info to a title), it would be nice to be able to load some versions of it from an external data provider (database, service, flat file...).

It may be achieved by using a new jinja filter like :
{{collection.title|enrich("title", collection.id, collection.lang)}}

Which is then linked to a new enhanced resolver :

class MetadataEditorialResolver()
    def find(data_name, coll_id, coll_lang):
        if data_name == "title":
            get_data_from_sqlite(data_name, coll_id, coll_lang)