The goal of this branch is to introduce a new hierarchy
of reader superclasses that make it easier to develop readers
by implementing / hiding some of the common functionality readers
have. This includes things such as file series as time series,
file series as partitions, caching etc. In collaboration with
a new executive (vtkReaderExecutive), the reader superclasses
implement much of the hard work and provide a simple API for the
subclasses to implement. For example, a parallel reader may
only have to implement 3 methods: GetMesh(), GetPoints() and
GetArrays() to get support for file series as time series and
caching (not implemented yet). This functionality is demonstrated
by making the Plot3D reader subclass from the new superclass.
The testing is automatic since there are numerous tests using
Plot3D files.