Add required sections to pom.xml for deployment

See

	https://docs.sonatype.org/display/Repository/Central+Sync+Requirements

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Build -source artifacts when releasing

As per OSS Sonatype guidelines:

https://maven.apache.org/guides/mini/guide-central-repository-upload.html

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Build -javadoc artifacts when releasing

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Add the OSS Sonatype parent information

This is the most convenient way to specify the repository information
required for staging to the OSS Sonatype artifact repository (which is
the way to get CPPTasks-Parallel into Maven Central).

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