apsbss: add "next" subcommand

[prjemian]

For the apsbss command, in addition to the list: {beamlines,current,cycles,esaf,proposal,clear,setup,update,report}

Can you add a next subcommand? This would be like current, but returns info about the next proposal/ESAF scheduled on the beam line. Particularly important would be proposal number, ESAF number, and start time. This could be used to automatically fill in information when a new experiment starts.

Thanks, Jon Tischler!

[prjemian]

Possibly related to #348.