Fixed the global counting of unread messages. This makes the "unreadCount"
variable in storage to stay in sync with the sum of unread messages in each
conversation. To achieve this, the controller_view updates the global
variable whenever messages are received or read.
Encapsulate the global conversation cache collection against accidental
access, avoiding the data-clobbering bug fixed in previous commit.
Also move some one-off program initialization code from panel controller
to background.js
// FREEBIE
ody
lilia