Add uninstallation compatibility to 2.1.0
This also deletes files that were installed by previous versions of gpg4win * src/uninst-gnutls.nsi: Remove libgnutls-openlss-26.dll * src/uninst-qt.nsi: Remove files provided in old qt package * src/uninst-kleopatra.nsi: Remove various files installed by kdesupport, kdelibs et. al