Bump the SciJava POM version

... so it uses the latest license-maven-plugin version.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Update README.md to reflect imagej-maven-plugin's existence

While at it, also point to Fiji's Wiki page on debugging.

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