takers: ignore makers with more than max_offers_allowed offers

[AlexCato]

The option is configurable and defaults to 15.

Implemented as discusses in #711 and waxwing/belcher on IRC.

I'll build the overlapping offer checks on top of this soon.

[coveralls]

Coverage increased (+0.02%) to 77.409% when pulling 00ae19b on AlexCato:maker_offer_checks into 3756cc4 on JoinMarket-Org:develop.

[AdamISZ]

Looks good to me, utACK - assuming the sql works OK (well, obviously it's OK we have virtually the same call there already).

Also, I think 15 is reasonable. I wouldn't object to 5-10 either. But I think I'm more influenced by our low-bandwidth message channel (public IRC), it isn't necessary. Anyway ignore that, bikeshedding :)

We could consider a self.msgchan.send_error message to signal to the maker that they were banned?

[BlinkyStitt]

Will the orderbook also ignore these makers with these changes, or do we need more code for that?

[AdamISZ]

@wysenynja do you mean ob-watcher? Yes, the on_order_seen callback is in the OrderbookWatch class, and the filter is applied there. Whether that's good or bad, don't know, but then ob-watcher isn't too huge of a deal really.