CDFTOOLS before major modifications

CDFTOOLS v3.0.0

This release is the last release which support different mesh_zgr format as input. Further development requires simplication and modification in the treatment of the vertical metrics, in particular for time variation of e3.

A new convertion tool will be available to port old-type mesh_zgr files to the supported one.

Version v3.0.0 can be used with old-type mesh_zgr files.