We were closing the event QueuedChannel objects in the wrong place;
they should have been closed on test teardown, not on stopBridge
(which was just a test action and wasn't always called).
In order to make the events more scalable, i replace all the
QueuedChannel objects with a single event collector, which would
create QueuedChannels on demand when it receives an event of a new type.
Add missing Close calls.
Properly handle nil channel for `user.startSync`.
This patch also updated liteapi and Gluon to latest master and dev
version respectively.
There was a race condition internal to the go-smtp library.
In order to fix it, a version bump was necessary.
However, this significantly changed the library interface.
When an IMAP client appends a message to a mailbox, it can specify
which flags it wants the appended message to have. We need to handle
these in a proton-specific way; not-seen messages need to be imported
with the Unread bool set to true, and flagged messages need to
additionally be imported with the Starred label.
