Move windows distribution files to dist/windows

--HG--
rename : dist/LeoPackage.pmsp => dist/windows/LeoPackage.pmsp
rename : leo.nsi => dist/windows/leo.nsi
rename : dist/nsi-boilerplate.txt => dist/windows/nsi-boilerplate.txt
rename : nsi-install-files.txt => dist/windows/nsi-install-files.txt
rename : nsi-uninstall-files.txt => dist/windows/nsi-uninstall-files.txt