[IMP] mail: needaction/unread messages counters

Some UI changes:
  - Unread messages in chat are now displayed as needactions in the Discuss's
sidebar (badge with counter of unread messages, instead of simply bolding the
channel name).
  - The counter displayed in the navbar is now the sum of needactions and total
of unread messages in chat.
  - The counter displayed next to Inbox is still the needaction counter.

For consistency between tabs/browsers/devices, the channel_seen info is now
broadcasted, meaning that every tab/browser/device will be noticed.

Also now correctly increment the unread counter of a channel if the received
message is a needaction.

0 files changed, 0 insertions, 0 deletions