Issue #2543726 by damiankloip, Wim Leers, claudiu.cristea, voleger, dagmar,...

Issue #2543726 by damiankloip, Wim Leers, claudiu.cristea, voleger, dagmar, dawehner, amateescu, tedbow, FredCorreia, mgalalm, caseylau, jibran, dbjpanda, pcambra, Grimreaper, idebr, dmouse, larowlan, Berdir, chx, andypost, yched, fgm: Make $term->parent behave like any other entity reference field, to fix REST and Migrate support and de-customize its Views integration