app_queue: Add Lastpause field of queue member

Add time when started a the last pause for a queue member for
QueueMemberStatus ami event.

Also show accumulate time in seconds when started a pause for a queue
member to CLI command 'queue show'.

ASTERISK-16394 #close

Change-Id: I4b12aa3b2efa8d02939db3e13712510b4879865c