Do not even try to copy Eclipse files

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Make most of the POM settings truly optional

When the user leaves the properties at 'N/A', we should just skip the
corresponding sections in the generated pom.xml file.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>