Shell: Exported libshell key event and widget classes
libdeng2: Brought in more network functionality from Hawthorn

Protocol, IdentifiedPacket, and RecordPacket.
Shell: Added Link and Protocol classes

Link maintains a shell connection to a server. shell::Protocol is the
shell-specific network protocol.
libdeng2: Improved Socket opening, added better Address constructor

Sockets can now be opened asynchronously, with a signal emitted when
the connection is open.
Shell: TextWidget manual redrawing

Added a method for immediately redrawing and showing a text widget.
Shell|Fixed: Command line widget history

The history is now bash-like in that entries in the history can be
edited, but the edits are only remembered until Enter is pressed.
Shell: Added status widget

The status widget shows the status of the shell connection and
a summary of status information from the server, when connected.