Add Eclipse-SourceReference headers

[marchof]

All EclEmma and JaCoCo bundles should include Eclipse-SourceReference headers, so potential contributors can easily fetch the source code. This is currently not supported by Tycho.

Feature requests are:

• http://bugs.eclipse.org/380691
• https://issues.sonatype.org/browse/TYCHO-362

[Godin]

Depends on #43

[Godin]

Done in 4a77e40