jar editor: no magic numbers please

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>
jar editor: fix a resource leak of the printer

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>
fix #608: jar viewer v 2.0.0.REL produces corrupt "print" view

A famous off-by-one error...

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>
jar editor: make sure there is a blank line between print sections

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>
jar editor: do not print pointless '<no contents>' texts

Signed-off-by: Ferry Huberts <ferry.huberts@pelagic.nl>