PLAT-536 upgrade 8.2.1

[Saphyel]

Fixes https://jira.comicrelief.com/browse/PLAT-536 See changelog for 8.2.x

Manual deployment steps

• Make sure to run update-core in RND17

[pvhee]

@Saphyel is this being added as a patch as well? hard to find this since so many files changed :)

[Saphyel]

@pvhee for avoid that crappiness, I split this into 3 commits, check the last one in order to see that patch! :D

[pvhee]

Cool, had missed this!

[pvhee]

@gusliedke @AndyEPhipps @Heleen-cr this core update also updates the followign JS libs :

- Updated vendor libraries:
    * Updated to jQuery 2.2.3.
    * Updated to Twig 1.24.
    * Updated to CKEditor 4.5.11.
    * Updated to Symfony Routing 1.4.0.
    * Updated to Stack/Builder 1.0.4.
    * Updated to Guzzle 6.2.1.

Can you verify that our JS code will work correctly with these updated libs? Not worried about CKEditor but we should definitely verify jQuery and Twig

[AndyEPhipps]

@pvhee will check this out locally, I can't see the jQuery update borking anything really

[pvhee]

@AndyEPhipps you can also use the platform.sh url to just review functionality that relies on jquery

[AndyEPhipps]

@pvhee : tested on plat.sh env, all seems well; custom ESU and nav JS all fine, Panelizer stuff fine, Twig seems to be fine (no broken styles, so all functions/logic working as before). Have done the same on the RND17 test env will the same outcome