Factory documentation

The documentation of the factories are deprecated for the TYPE name rule (still capitals, they are now a copy of the class name).

added Idea documentation labels

assigned to @jsola

FactoryBase doc will explain how to specialize it to create specific factories (factory specialization).

It will also explain how to use the specific factory once created (the API).

created merge request !350 (merged) to address this issue

mentioned in merge request !350 (merged)

added To Do (release) label and removed Idea label

closed via merge request !350 (merged)

mentioned in commit 7e1c38d3