Refine input type of Centroid() builtin.
Refine input type of Centroid() builtin.

It now accepts any collection, which is too wide, but there
is no way to specify 'Entities' as a group in the current SymbolTable
implementation.

babrodtk/equelle,sintefmath/equelle,atgeirr/equelle,atgeirr/equelle,sintefmath/equelle,atgeirr/equelle,atgeirr/equelle,babrodtk/equelle,sintefmath/equelle,babrodtk/equelle,babrodtk/equelle,sintefmath/equelle,atgeirr/equelle,babrodtk/equelle,atgeirr/equelle,atgeirr/equelle,babrodtk/equelle,atgeirr/equelle,sintefmath/equelle,sintefmath/equelle,babrodtk/equelle,sintefmath/equelle,sintefmath/equelle