(bug 44385) move jquery.collapsibleTabs module to Vector extension

(bug 44385) move jquery.collapsibleTabs module to Vector extension

It was entirely Vector-extension-specific (so very unlikely to have
been used by anything external), deeply interconnected with the
extension (its internal functions were overwritten by a script from
it, making it even more incompatible with other uses), and this
functionality (being really a partial workaround for low-res issues
with the skin) belongs to the extension instead of the skin anyway.

Corresponding Vector extension change: Ic6b622279

Change-Id: I7c0f42d922b20741f66014eea0a7593bc1950e0e