Support for away status in Jitsi presence Operation Set.
Created separate class for IRC presence management.
Added markers for future work w.r.t. Away-support.
Simplification.
Fire message received upon receiving RPL_AWAY message from server.
Removed old (commented) code.
Set correct IRC away icon in images.properties.
Added TODO for future work w.r.t. presence of chat room members.
Added TODO marker w.r.t. needed Jitsi infrastructure.
Tweaking presence communication.
Fine-tuning away behaviour: empty message implies no message.