[releng] Package structure adjusted

Change-Id: I0257ebd393a14a3f40f4a6d9587ae5f48c280419
Signed-off-by: Yasser Aziza <yasser.aziza@gmail.com>
Signed-off-by: Andreas Sewe <andreas.sewe@codetrails.com>
[docs] Contributing.md updated, javadoc improved

Change-Id: I3f3771f46b4c2647e61af9f84b1e29b711d588f4
Signed-off-by: Yasser Aziza <yasser.aziza@gmail.com>
Signed-off-by: Andreas Sewe <andreas.sewe@codetrails.com>