added helper "action.d/helpers-common.conf", and `_grep_logs` part-command for actions needed grep logs from multiple log-files
test cases: executing of some complex actions covered
* 'grep-m1k' of github.com:szepeviktor/fail2ban:
Limit the number of log lines in *-lines.conf actions
Conflicts:
ChangeLog -- took both versions and adjusted the new one
for -n 1000 change