Use external tablesorter

Makes use of the jquery.tablesorter instead of the homemade one.

Also:

• Drop local jquery in favour of cdnjs jquery
• Drop unused stepcarousel js
• Add missing jquery dependency to page using bootstrap.js
• Replace tools.wmflabs.org/static with tools-static.wmflabs.org/cdnjs

These are preparatory steps for enabling ESlint.

Bug:T179216
Change-Id: I5b606a223daf786db62d0240a3c8d3a673fe7441