os_alert: Added DB serialization.

Moved data structures into os_alert.h.

Refactored os_cmd_alert_add into parse_alert so that it can be used for
deserialize.
os_alert: Added USER criteria.

The nick and user criteria both use the same underlying type:
alert_pattern_criteria_t, but with different constructors.
os_alert: The NOTICE action now shows the alert id.
os_alert: Add GECOS criteria.

pattern_display now handles multi-word patterns.
os_alert: add HOST criteria.
os_alert: Add IP criteria
os_alert: formatting
os_alert: Add MASK criteria.
os_trace: Add SERVER criteria.
Add channel_joined and channel_parted.

Remove hooks in _moddeinit.
Add event handlers for identify, register, drop, and sethost
os_trace: add identified criteria
os_alert: Add channel criteria