nds2-client-swig tarball needs a copy of the license file

Since nds2-client-swig is licensed under GPL, a copy of the license needs to be included in the tarball. This is done for the core nds2-client package, but not for the SWIG bindings.

The license should also be included in the RPMs by adding the following entry under %files for each %package:

%files -n ...
%license COPYING

Something similar should probably be done for debian, but I don't know what.