[Tagging] Disambiguation between statue and sculptural group

[Daniel Capilla]

Hi,

I have proposed to clarify in the wiki the use of the tag 
"artwork_type=statue" by explaining the difference between a statue and 
a sculptural group. In the community discussion forum you can see some 
examples illustrating the difference. [1]

I propose to update the documentation to differentiate between 
"artwork_type=statue" (sculpture of one person/animal) and 
"artwork_type=sculptural_group" (sculpture of group representing two or 
more people/animals).

[1] 
https://community.openstreetmap.org/t/disambiguation-between-statue-and-sculptural-group/97828