Use separate column for zero in output of stg series -e

This will make the output more regular and easier to parse. It no longer
overwrites the +/-/! status flag with a zero for empty patches, and
instead puts the zero before it.

Signed-off-by: David Kågedal <davidk@lysator.liu.se>
Signed-off-by: Karl Hasselström <kha@treskal.com>