Fixing bugs sanitization bugs introduced in 2.3

git-svn-id: https://plugins.svn.wordpress.org/document-gallery/trunk@1044508 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updating changelog with 2.3.1 changes

git-svn-id: https://plugins.svn.wordpress.org/document-gallery/trunk@1044511 b8457f37-d9ea-0310-8a92-e5e31aec5664