Add new system properties/environment vars classes to autogen docs

Just flagging this so it can be integrated into autogen docs somehow - it'd be good to have this available online somewhere
https://github.com/deeplearning4j/deeplearning4j/tree/master/deeplearning4j/deeplearning4j-common/src/main/java/org/deeplearning4j/config

ND4J will be getting the same treatment soon (edit: PR here: https://github.com/deeplearning4j/deeplearning4j/pull/6021)

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