Port most of the Python zgydump tool to C++.

The ZgyDump tool displays meta information from one or more ZGY files. Now also available in the C++ version on Linux and Windows. Not just Python.

Somewhat less information is shown in the C++ version because OpenZGY/C++ does a better job of hiding internal details. The --offsets option doesn't work at all. Apart from debugging the applications are not supposed to know or care where in the file a given brick is to be found.

The tool is similar to MetaInspector.