Issue #2421263 by alexpott, formatC'vt, kim.pepper, andypost, larowlan, chx: Potential data loss: concurrent (i.e. by different users) node edits leak through preview

Issue #2313931 by Berdir: Merge ['controller'] with ['build_info']['callback_object'] and add a method for it.

Issue #1510544 by swentel, Bojhan, Gábor Hojtsy, merlinofchaos, Cottser, Wim Leers, plopesc, aspilicious, sannejanssen,  larowlan, tim.plunkett, nod_: Fixed Show previews in front-end theme, able to select different view modes.