Added 'filter' support to position function; Made sure sort script can depend on the value of the field itself.

Cleaned up some things, why is a blank image not thread safe?

git-svn-id: svn://svn.code.sf.net/p/magicseteditor/code/trunk@548 0fc631ac-6414-0410-93d0-97cfa31319b6

src/data/field/text.cpp

@@ -127,12 +127,13 @@ String TextValue::toString() const {
 	return untag_hide_sep(value());
 }
 bool TextValue::update(Context& ctx) {
-	Value::update(ctx);
+	updateAge();
 	WITH_DYNAMIC_ARG(last_update_age,     last_update.get());
 	WITH_DYNAMIC_ARG(value_being_updated, this);
 	bool change = field().default_script.invokeOnDefault(ctx, value)
 	            | field().        script.invokeOn(ctx, value);
 	if (change) last_update.update();
+	updateSortValue(ctx);
 	return change;
 }