Fixed a missing initialization.
A port conn is now upgraded to an yb conn only if the port can't be used.

This fixes a problem where selecting a port connection, whose programmer
type is set to shupito, into a terminal fails.
PortShupitoConn will now request the descriptor on second connect too.
USB ACM line params will be set before the conn is marked connected.

This makes any yb conns over the ACM port request descriptors only after
the line is prepared.
Disabled double-buffering in ACM conns.

The bug in the driver seems to be triggered even with only two buffers.
Removed Connection::SetOpen.
Added ThreadChannel<void> specialization.
USB ACM connection will now flush before completing a disconnect.

This allows a shupito connected via a tunnel through another shupito to be
disconnected cleanly.

A new connection state, st_disconnecting, was added to support the
disconnect flush correctly.
Added proper flush to usbshupito23conn.
usbshupito23conn will auto-disconnect after name persist.
Fixed a crash when shupito22 is removed which connected.
shupito22 fw version is displayed in chooseconndlg when available.
Fixed flush for ACM and shupito22 connections.
Merge branch 'master' of github.com:Tasssadar/Lorris

Conflicts:
	src/connection/shupitoconn.cpp
Merge pull request #14 from avakar/master

Fixy