Add IsFirst/IsLast methods to match SS5 conventions (closes #1274) #1143

Job	Run time
CI / Generate matrix	12s
CI / Context	1s
CI / 8.1 prf-low mysql57 phpunit all	3m 19s
CI / Check governance	0s
CI / 8.2 mariadb phpunit all	2m 48s
CI / 8.3 mysql80 phpunit all	3m 25s
CI / 8.1 mysql57 phplinting	2m 18s
CI / 8.1 mysql57 endtoend root job1	11m 30s
CI / 8.3 mysql80 endtoend root job1	8m 36s
CI / 8.1 mysql57 endtoend root job2	7m 41s
CI / 8.3 mysql80 endtoend root job2	8m 17s
CI / 8.1 mysql57 endtoend root job3	9m 20s
CI / 8.3 mysql80 endtoend root job3	9m 59s
CI / 8.1 mysql57 endtoend root job4	9m 32s
CI / 8.3 mysql80 endtoend root job4	9m 6s
CI / 8.1 mysql57 endtoend root job5	7m 6s
CI / 8.3 mysql80 endtoend root job5	6m 13s
CI / 8.1 mysql57 endtoend root job6	7m 51s
CI / 8.3 mysql80 endtoend root job6	8m 17s
CI / 8.1 mysql57 endtoend root job7	11m 18s
CI / 8.3 mysql80 endtoend root job7	13m 10s
CI / 8.1 mysql57 js	4m 24s
CI / 8.1 mysql57 doclinting	2m 33s
CI / Dispatch tag patch release	0s
	2h 26m 56s

Provide feedback