new options for jail introduced addfailregex/addignoreregex #867

feature request (#867): new options for jail introduced `addfailregex`/`addignoreregex`: extends regex specified in filter (opposite to `failregex`/`ignoreregex` that overwrites it);

BF: failregex declared direct in jail was joined to single line (specifying of multiple expressions was not possible);

Ahh, I missed that `addfailregex` is a jail option, not a filter option.

What about if `addfailregex` was added as a filter option instead? Then `addfailregex` could be added in a `.local` filter file to add regex definitions defined with `failregex` in a `.conf` filter file?