Update VisualEditor to master to pick up acb30c3

Deploys
* 586696f - ve.ce.MWBlockImageNode: Use this.constructor to refer to class (2 hours ago) <Timo Tijhof>
* acb30c3 - Fix the save button disappearing on certain pages in Firefox (2 hours ago) <Roan Kattouw>
* d4207eb - Localisation updates from http://translatewiki.net. (4 hours ago) <Translation updater bot>

Change-Id: Idc7b094f8eb2788c4845c9943e359f749d2479f2