restyle upload page

Use <fieldset> and <legend> elements
and abolish old <table>-based layout.
minor improvements to upload page
change form validation behaviour

Use HTML5 attributes to ensure all fields are filled in. Only
if not supported by the browser, use javascript. Shorten JS
code and put it all in upload.js file. Let the button enabled
if JS is disabled.
some restyling for login page

Use CSS instead of table-layout, use
<label> tags and add a reset button.
Fix user-autocomplete not to throw a
warning for registration page. Also
add a special stylesheet for the page.