porepare for release [skip-ci]

Doc/changelog.docu

@@ -7,7 +7,7 @@
 <!-- --------------------------------------------------------------------- -->
 
 
-<tr valign=top><td><b>8.0</b> (?/?/?)</td><td>
+<tr valign=top><td><b>8.0</b> (2019/02/21)</td><td>
 
 <b>Breaking changes:</b>
 <ul>

release.howto

-1. check files, build on windows,mac,linux with cmake
+1. check files, build on windows,mac,linux with cmake (-> Done by CI)
 2. check files with release numbers:
    cmake/FindOpenMesh.cmake
    Doc/changelog.docu
    src/OpenMesh/Core/System/config.h
    README
    VERSION
-3. Tag the current version in the svn (checkout, remove .svn readd as tag)
-4. Create HTML-Documentation in OpenMesh/Docu/ (!)
-5. Create tar-ball and zip-archive
+3. Tag the current version in the git 
+4. Create HTML-Documentation in OpenMesh/Documentation (!)
+5. Create tar-ball and zip-archive ( -> Done by CI)
    > tar cvzf OpenMesh-<version>.tar.gz OpenMesh-<version>/
    > tar cvjf OpenMesh-<version>.tar.bz2 OpenMesh-<version>/
    > zip -9 -r OpenMesh-<version>.zip OpenMesh-<version>/