Create/store endpoint state - create history/graph

[mStirner]

Would be nice to create a snapshot of a endpoint state every then and now.
Could be enabled on a endpoint with a label, e.g. oh.history.enabled=true (and to specify only specific state oh.history.states=6676f8105e3e7f0bde2c4137,6676f8154b559a92b0adbbf5).

With a cronjob, could then be "snapshot" create of all endpoint states (values).

Related to: OpenHausIO/frontend#117