Remove Maven profile 'release-sign-artifacts'

Is redundant because the pom parent oss-parent has a profile named
'sonatype-oss-release'.
Add notes for performing a release to Maven Central
Roll back version to SNAPSHOT

So that we can run $ mvn release:prepare
Version should be 4.08, not 4.0.8
Add github repo url to make maven-release-plugin work

It needs to be able to push somewhere. I don't have write access to the
opendis sourceforge svn.
Ignore maven-release-plugin temp files
[maven-release-plugin] prepare release srm-4.4.0