Additional epoch analytics keys

[Ivshti]

Currently, additional stats (AIP23) are persisted, but not all of them are segmented by epoch

Additional keys that need to be segmented by epoch:

• publisher to ad unit
• publisher to hostname
• ad slot to country - that way, we can get specific per-country reports for each ad slot

Additionally, we need a script that cleans up the epoch keys for all but the last N epochs - to make sure that the redis db does not get too full.

Finally, consider dropping some of the advanced analytics - the ones that seem redundant

• PublisherToAdSlotEpoch - not used, plus each ad slot is already associated with a publisher; so just adslot->epoch is fine, or ad slot hour - double check with @GTitova

[Ivshti]

irrelevant cause of https://github.com/AdExNetwork/aips/issues/75