Made retistructdemos a Suggests

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/retistruct@1312 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Updated user guide

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/retistruct@1313 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Updated license to CC BY-SA 4.0

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/retistruct@1314 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Updated user guide

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/retistruct@1315 edb9625f-4e0d-4859-8d74-9fd3b1da38cb