(cherry picked from commit a92f817f)

Issue #2811725 by mpdonadio, paulanders, jhedstrom: Error when render Datetime Range field: Error: Unsupported operand types

(cherry picked from commit 36bc9121)

Issue #2796151 by mpdonadio, jhedstrom, myLies, vijaycs85, lomasr, alexpott, Gábor Hojtsy, penyaskito, catch, xjm: Date range separator should be translatable

(cherry picked from commit a55967de)

Issue #2786583 by claudiu.cristea, jhedstrom, effulgentsia: Create a base class for DateTimeFieldTest and DateRangeFieldTest and move common code into it

(cherry picked from commit f03979cc)

Issue #2161337 by mpdonadio, darrick, swentel, effulgentsia, YesCT, xjm, Berdir, tim.plunkett, pguillard, SKAUGHT, sylus, jonathanjfshaw, FluxSauce, DuneBL, jhedstrom, dawehner, generalredneck, pjonckiere, borisson_, Gábor Hojtsy, webchick, miwayha: Add a Date Range field type with support for end date

(cherry picked from commit b1656002)