[dev] patch: implement "new message!" note in AgentQueueView

Hi, This patch lifts the "New Message!" message logic from AgentMailbox and adds it to AgentQueueView. I'd like it considered for inclusion into the OTRS codebase. Feedback is, as always, appreciated. Thankyou, Adrian -- Adrian Chadd The University of Western Australia CRICOS: 00126G Ph: +61 8 6488 2574 Mob: +61 421 597 819