Merge branch 'jquery2' into 'master'

Upgraded jQuery to version 2

## What does this MR do?

Upgrades jQuery to 2.2.1. 

Had to include the task_list JS file directly as it includes jQuery 1 directly https://github.com/github-archive/task_list/blob/master/app/assets/javascripts/task_list.coffee#L8 so when we change jQuery to `jquery2` it was including both jQuery 1 & 2.

## Are there points in the code the reviewer needs to double check?

For any JS errors

## What are the relevant issue numbers?

Closes #12440

See merge request !4384