The terminal_mux server is able to provide multiple terminal sessions over one
terminal-client session. The user can switch between the different sessions
using a keyboard shortcut, which brings up an ncurses-based menu.

The terminal sessions provided by terminal_mux implement (a subset of) the
Linux terminal capabilities. By implementing the those capabilities, the server
is interchangable with the graphical terminal ('gems/src/server/terminal').
The terminal session used by the server is expected to by VT102 compliant.
This way, terminal_mux can be connected via an UART driver with terminal
programs such as minicom, which typically implement VT102 rather than the Linux
terminal capabilities.

When started, terminal_mux displays a menu with a list of currently present
terminal sessions. The first line presents status information, in particular
the label of the currently visible session. A terminal session can be selected
by using the cursor keys and pressing return. Once selected, the user is able
to interact with the corresponding terminal session. Returning to the menu is
possible at any time by pressing control-x.

