Use of default names

There are predefined default names for the following objects: Experiment, DataSet, Diffractometer, UnitCell, Monochromator, Goniometer, Axis, Detector, PeakCollection. This seems to be a consequence of defining a default constructor for most of these objects. In 99% of these cases, the object should not be default-constructible, and should require a name, since the default name can lead to instances of confusing provenance.