Update legendgraphic.rst

fix GEOS-6737
Update vendor.rst

fix GEOS-6756
Merge pull request #818 from Martin-Wegner/patch-2

Update vendor.rst
Merge pull request #817 from Martin-Wegner/patch-1

Update legendgraphic.rst
Merge branch 'master' of git://github.com/geoserver/geoserver