Configure Maven build to capture test coverage using jacoco.
Add new org.eclipse.jgit.coverage Maven module to aggregate
jacoco test coverage results and generate test coverage HTML report at
org.eclipse.jgit.coverage/target/site/jacoco-aggregate/index.html
See https://www.eclemma.org/jacoco/trunk/doc/maven.html
Change-Id: Iaeec4033e448ebc16965c05ab54109c4155a307a
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>