keep the content of the submition form when its not validated, or try some ajax realtime pre-validation

[SuperUserNameMan]

hi,

yesterday, i tried to submit something to the asset lib.

I filled all the form inputs except the thumbnail textboxes because they were marked "will be removed".

When I submited the form, it showed an ERROR page complaining about the missing thumbnails.

And when I went back to the form, it was empty.

And because I was too lazy to fill it again, I just gave up.

So it would be cool if the form was javascriptly verified before actual submission, or if it was pre-filled with the previous content when error happen after submission.

[bojidar-bg]

Tagging as 1.0 not since it should be too hard to do, but since it isn't a release-blocker.