Feature request: enable UberData.extractContent to use @Relation itemRelation in adition to Class.getSimpleName

[lcampos21]

Right now UberData will use the class name for each item of a collection ignoring the @resource(itemRelation="name").
"data": [ { "name": "className", "data": [ {...} ] }, { "name": "className", "data": [ {...} ] } ]