Fix disappearing transferlist list when zooming in the browser

When the page is zoomed in the browser, the transferlist doesn't fit
in the page and is moved below the left column, disappearing completely.

Allow elements to overlap the handle to prevent this from happening.

The error message is moved in the status bar since it's wrongly placed
because of the overlap.

Closes #603.
Use fake tristate checkbox on IE < 9 only
Reduce font size of priority combo boxes

They were too big in some cases (e.g. Firefox on Linux).
Remove XML Encoding from HTML files
Restricts hacks and workarounds to IE < 9
Workaround to make invisible buttons clickable on IE
Bump Internet Explorer compatibility
Minor UI changes to upload window

Fix also the window auto-close when uploading torrent for some browsers.
Fix errors in width and height calculations

border-left/right/top/bottom are not numbers.
Fix panel height calculation in Opera
Drop Firefox specific code

This change improves the responsiveness while resizing panels.
The code was intended to fix bugs in really old versions of Firefox.
Add missing images and fix few paths

These images are used in CSS rules, but are missing.

Images taken from MochaUI git repo.
Center images in top menu
Rotate expand image to better suit the its use in the UI