Add guard for invalid Python environment
More reordering of package includes
Turn off PARAVIEW_BUILD_QT_GUI

We don't need to build the ParaView GUI
The target for building Python needs to be PythonInterp
Ensure gdal build picks up correct version of netCDF
Ensure built Python is picked up for Cython build
Add CURL version to add_sb_package(...) call
Ensure HDF5 build used correct version of zlib
zlib => ZLIB so find_package(...) will work

Also include the zlib version
Add CURL version to add_sb_package(...) call

Also make SYSTEM the default
add_sb_package => add_sb_python_package for numpy
Add version to add_sb_package(...) call for wget

Also make default SYSTEM