Add support for vector scalars and strings for netCDF.
I can see scalars in the View->Scalars dialog and strings in the debugger as well as in labels.

We only need to upgrade a bit the View->Strings dialog and do the same for other primitives (matrices, ...) and it will start looking real good for that data source :-)

I am also wondering whether I have to explicitly delete the *att and *var objects created in those functions, or if they get cleared as soon as we leave the scope.

Please check because that would mean a memleak (I haven't done it for now).