These are features which have been requested for later versions of
Sunsort, or are features which are easy to add.

0) Find someone to maintain Sunsort.

1) More debug/verbosity control.

2) Add writing support to ANU format data.

3) Allow more than 4 spectra at once in 1d viewer - allow a choice of
   several predefined layouts.

4) Finish the manual.
