private static void handleLegacyValuesOnSet(final int keyId) {
        //if a new key is actively set for the first time, its existing legacy values are no longer needed
        for (String legacyKey : getLegacyPreferenceKeysFor(keyId)) {
            final String value = getStringDirect(legacyKey, null);
            if (value != null && !value.startsWith(LEGACY_UNUSED_MARKER)) {
                putStringDirect(legacyKey, LEGACY_UNUSED_MARKER + value);
            }
        }
    }
gets current setting for a persistable uri or null if unset
should be called by BackupUtils.restoreInternal only
main/src/main/java/cgeo/geocaching/settings/Settings.java