Improve convergence output.
 - Add CNV{W,O,G} to output.
 - Make output a bit tighter.
 - Avoid printing extra newline and header for each iteration.
Fix: change a CNVO to CNVW in header printout.
Further output refinement.
Fix convergence output header (again).
Merge pull request #231 from atgeirr/modify-convergence-output

Improve convergence output.