I'd like to switch these to specifying in particular what items we are importing.  

Mostly because it allows for the option of adding some helper functions in the future that we might not want to import in to the full `galsim` namespace.  There aren't any currently in these files, but I think it's helpful to keep to that pattern so we have to consciously make a decision to add items to the `galsim` namespace rather than have things pass in accidentally is someone adds some functions to these files someday.