pdf viewer: default white background for generated images

git-svn-id: http://www.pimcore.org/svn/pimcore/private/core/trunk@2890 1f8fe7d8-47f0-464c-8d0a-336f4953ab05
localstorage "pimcore_opentabs" should be cleared when File -> Close all tabs

git-svn-id: http://www.pimcore.org/svn/pimcore/private/core/trunk@2891 1f8fe7d8-47f0-464c-8d0a-336f4953ab05
build auto version ...

git-svn-id: http://www.pimcore.org/svn/pimcore/private/core/trunk@2892 1f8fe7d8-47f0-464c-8d0a-336f4953ab05