#411 More functions for set and get in XoopsForm classes

[irmtfan]

Now some actions cannot be done in some xoopsform classes.
eg: we cannot disable an option in a select box or checkbox form.
even for a input text form we should do some tricky ways using setExtra function.

It is very needed.

more discussion here:
http://xoops.org/modules/newbb/viewtopic.php?post_id=351477#forumpost351477