Allow moving a node to another location in the same document.

Add a useful tree manipulation function allowing to move a node to another
parent. This is simpler than copying it and also avoids problem with
namespace definitions which are duplicated when the nodes are copied.
Just fix a typo in the NEWS file.
Increase version to 0.7.2.

Increase version in preparation of adding new APIs: this will allow to
determine if they are available or not.