add possibility of skipping tables with useless data

git-svn-id: https://plugins.svn.wordpress.org/updraftplus/trunk@848393 b8457f37-d9ea-0310-8a92-e5e31aec5664
add possibility of skipping tables with useless data

git-svn-id: https://plugins.svn.wordpress.org/updraftplus/trunk@848394 b8457f37-d9ea-0310-8a92-e5e31aec5664