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);

Hmm, does this mean that both `failregex` and the new `addfailregex` command line option append rather than replace? If so, why is there a need for creating the new `addfailregex`? Or is that necessary due to the Python config parser?