ENH add canInit method and CAN_DEV_GRAPHQL permissions #331

Job	Run time
CI / Generate matrix	10s
CI / Context	2s
CI / Check governance	1s
CI / 8.1 prf-low mysql57 phpunit all	3m 19s
CI / 8.1 mysql57 phpunit all	3m 14s
CI / 8.2 mysql80 phpunit all	4m 30s
CI / 8.1 mysql57 phplinting	2m 21s
CI / 8.1 mysql57 endtoend asset-admin	6m 23s
CI / 8.1 mysql57 endtoend versioned-admin	5m 41s
CI / 8.1 mysql57 endtoend silverstripe-elemental	10m 28s
CI / Check unreleased changes	0s
CI / Patch release	0s
	36m 9s

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