SA-CORE-2018-003 by mlewand, wwalc, jcisio, Kyaw Min Thein, Wim Leers, larowlan, dawehner, drpal, xjm

(cherry picked from commit b839be0a)

Issue #2342633 by Wim Leers, wwalc: Fixed CKEditor context menu broken due to an error in the drupalimage plugin.

Issue #2317821 by Wim Leers, nod_ | wwalc: Do not show a dialog about changing formats when there is no content.

Issue #2099741 by Wim Leers, wwalc, mr.baileys, eaton, dstol, nod_, effulgentsia: Protect WYSIWYG Editors from XSS Without Destroying User Data.

Issue #1933914 by Wim Leers, Bojhan, quicksketch, wwalc: Enable CKEditor in the Standard install profile's 'Full HTML' text format.