PT37838221: Add fail2ban as sipXecs core service

- added new Security global feature, enabled by default (unamanged setting too). When enabled System > Security menu is shown
- added SIP based security rules: DoS (enabled by default, that is ban all IPs considered DoS attackers), SIP methods
- each rule can be configured with IPs to ignore, Ban time in seconds, number of failures before ban and time period for counting failures
- each rule is represented by a fail2ban filter, action to take is ban all ports, all protocols from that IP
- added alarms for IP banned / unbanned events