[BUGFIX] Prevent bouncing fileupload field

[BUGFIX] Prevent bouncing fileupload field

After a file is selected in the first step of an upload,
the options are shown and the fileupload field is resized
to a much smaller field. In Chrome and other browsers
this field bounces to an area above the form.

Use relative positioning and fixed heights to prevent this
UI glitch.

Refs #71