Pakfire: Add new command line argument "status"

Pakfire: Add new command line argument "status"

This enables Pakfire to return a Status-Summary for the Current Core-Update-Level, time since last updates, the availability of a core-/packet-update and if a reboot is required to complete an update. This can be used by monitoring agents (e.g. zabbix_agentd) to monitor the update status of the IPFire device.

Signed-off-by: Alexander Koch <ipfire@starkstromkonsument.de>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>