It is no longer needed to keep track of conversions between RVP6 (which might
actually represent dBZ data) and DBZ. Those behaved differently depending on
the product type.

This includes local radar images. DataZ and AtZ() is introduced for 3D CAPPI
products.  Data and DataZ are both slices of PlainData, stripping elevation
views and splitting concatenated layers.
A lookup catalog is neccessary, as runlength decoding requires dimension
information, that is not specified in the local picture product headers.

An identificated grid is now indicated by the HasProjection flag.

off-by-one error witnessed by improved translation tests
in commit c503d9d7

Test Translate() against expected Fortran output