improved deactivation and uninstallation 

git-svn-id: https://plugins.svn.wordpress.org/bibsonomy-csl/trunk@989465 b8457f37-d9ea-0310-8a92-e5e31aec5664
release 2.0.0

git-svn-id: https://plugins.svn.wordpress.org/bibsonomy-csl/trunk@989475 b8457f37-d9ea-0310-8a92-e5e31aec5664