Capture recordHit metrics for all new auctions (total) and per exchange ...

...as well as ignored per exchange.  Refactor to introduce a helper function in Auction: const char * exchangeName() const.

Proposal - follow up with another branch to harmonize the metric naming convention:
* bid -> bids
* exchange.*.requests -> exchange.*.auctions
* exchange.*.ignoredRequests -> exchange.&.ignoredAuctions