Changed default labeling to automatic (requested by Markus). [needs backport]

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24845 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Make sure our preferences are valid against our schema

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24846 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e