Missing environment variables for `mongo-selective-pump` in documentation

[buraksekili]

At the moment, there are no environment variables regarding mongo-selective-pump documented in README

tyk-pump/README.md

Lines 422 to 435 in 7af2a45

	###### Env Variables
	```
	TYK_PMP_PUMPS_MONGO_TYPE=mongo
	TYK_PMP_PUMPS_MONGO_META_COLLECTIONNAME=tyk_analytics
	TYK_PMP_PUMPS_MONGO_META_MAXINSERTBATCHSIZEBYTES=80000
	TYK_PMP_PUMPS_MONGO_META_MAXDOCUMENTSIZEBYTES=20112
	TYK_PMP_PUMPS_MONGOAGG_TYPE=mongo-pump-aggregate
	TYK_PMP_PUMPS_MONGOAGG_META_USEMIXEDCOLLECTION=true
	TYK_PMP_PUMPS_MONGOAGG_META_STOREANALYTICSPERMINUTE=false
	TYK_PMP_PUMPS_MONGOAGG_META_AGGREGATIONTIME=50
	TYK_PMP_PUMPS_MONGOAGG_META_ENABLESELFHEALING=true
	```

Also, according to docs, mongo-selective-pump.name is deprecated. This field might need to be updated.

tyk-pump/README.md

Line 411 in 7af2a45

"name": "mongo-pump-selective",