This reverts commit 3c76c819.

Issue #2898808 by effulgentsia, larowlan, drpal, droplet, cilefen: [regression] With jQuery3, modal tour tips lose their grey background and centering

Issue #2533498 by Manuel Garcia, effulgentsia, nod_, Dom., larowlan, drpal, Wim Leers, droplet: Update jQuery to version 3

Issue #2809427 by gnuget, Manuel Garcia, Wim Leers, nod_, sergeiimalyshev, tedbow, effulgentsia: Update jQuery UI to 1.12

Issue #2831442 by Wim Leers, tkoleary, tstoeckler, mattlt: Switch to CKEditor 4.6's new "Moono-Lisa" skin

Issue #2828494 by thpoul, Wim Leers, mlewand, tstoeckler, xjm, Tade0: Update CKEditor library to 4.6

Issue #2239419 by thpoul, Wim Leers, webchick, maczizek, xjm, mlewand, Jeff Burnz, tstoeckler, Tade0, Bojhan, yoroy, tkoleary, darketaine, hass, sun, maxilein, nod_, alexpott, Feuerwagen, oleq: Include CKEditor's AutoGrow plug-in

Issue #1993928 by BarisW, Wim Leers, thpoul, effulgentsia, mgifford, Gábor Hojtsy, Hanno, Pancho, Bojhan: Language of parts: Introduce a language toolbar button

Revert "Issue #1993928 by BarisW, Wim Leers, thpoul, mgifford, Gábor Hojtsy, Hanno, Pancho, Bojhan: Language of parts: Introduce a language toolbar button"

This reverts commit 11344070.

Issue #1993928 by BarisW, Wim Leers, thpoul, mgifford, Gábor Hojtsy, Hanno, Pancho, Bojhan: Language of parts: Introduce a language toolbar button

Issue #2480333 by Wim Leers, Elijah Lynn: Document how to use an unminified CKEditor build (for developing/debugging)

Issue #2485579 by ram4nd, droplet, nod_, MustangGB, evilfurryone, iMiksu: Update JS library picturefill to 2.3.1