Moved MultiSpat vignette to www/; revised DESCRIPTION

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/guerry@22 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Added mention of vignette here

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/guerry@23 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Removed R/thinnedSpatialPoly

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/guerry@24 edb9625f-4e0d-4859-8d74-9fd3b1da38cb