updated translation string

git-svn-id: https://plugins.svn.wordpress.org/p2-header-ad/trunk@817888 b8457f37-d9ea-0310-8a92-e5e31aec5664
added .pot file for translators
added German translation

git-svn-id: https://plugins.svn.wordpress.org/p2-header-ad/trunk@817892 b8457f37-d9ea-0310-8a92-e5e31aec5664