The user can start, stop and list sessions.
A session is defined to be a single streak of work, pretty much from sitting down to start to getting up and leave. The system needs to track the time the session started and the time the session ended. (So it can compute the length of the session.)
The following commands are necessary:
> txo start
txo start begins a new current session. If a session is already running, an error has to be output.
> txo end
txo end ends the current session. If no session is running right know, an error has to be output.
> txo list session
This lists all sessions. The output must contain the identifier of the session and the length.
> txo show SID
This prints further information about the session identifier by the identifier. if the session ID is not valid, an error has to be output. The information output must contain the beginning time, the ending time (in the user locale timezone), the identifier and the length of the session.
