feature 2929: strip metadata on configurable threshold


git-svn-id: http://piwigo.org/svn/branches/2.5@23498 68402e56-0260-453c-a942-63ccdbb3a9ee
next version is 2.5.2

git-svn-id: http://piwigo.org/svn/branches/2.5@23524 68402e56-0260-453c-a942-63ccdbb3a9ee