Node.getChildren() returns unmodif view. Closes #370.
Node.getChildren() returns unmodif view. Closes #370.

CompEvol/beast2,Anaphory/beast2,tgvaughan/beast2,tgvaughan/beast2,tgvaughan/beast2,CompEvol/beast2,tgvaughan/beast2,Anaphory/beast2,Anaphory/beast2,Anaphory/beast2,CompEvol/beast2,CompEvol/beast2