Enhance 'BadBotBlocker.php' for IP-adresses

[LarsRabe]

Triggered by this forum discussion https://www.webtrees.net/index.php/en/forum/help-for-release-2-1-x/37854-any-plans-to-block-certain-ip-adresses-from-trying-to-login I checked my logs for attackers.

Apart from the obvious suspects which can be blocked by the block_asn method, I also found attacks coming from IP-adresses of legit ISPs. In this case the block_asn method is too much.

Therefore I would lilke to see the BadBotBlock.php being enhanced by a block_IP method so a range of single IP-adresses can be blocked as well.