Summarising - build-sums

• Automatically updates summaries for changed logs
• Produces totals by months, years and totals. e.g.

  sums/
    1995-01-01.sumc  1995-01-02.sumc 1995-01-03.sumc
    ...
    1995-01.sumc
    1995-02.sumc
    ...
    1994.sumc
    1995.sumc
    ...
    total.sumc
  	

  for suffix sumc - generated by sum-counts.