SI-6471 Update jquery from 1.4.2 to 1.8.2

This reopens SI-6170 that was fixed by 1be1f76. I don't want to start
a revert war, but I see two reasons we should stick to newer jquerys:
 - they provide better compatibility to new browsers
 - having diagrams not working is much more annoying than having the
splitter not work

Author: VladUreche