ISPN-5024 Generate META-INF and blueprint services automatically

Fix Maven errors in Eclipse:
"Error(s) found in manifest configuration (org.apache.felix:maven-bundle-plugin:2.4.0:bundle:default-bundle:package)"

Caused by Include-Resource entries which are missing (they are generated using the 'script' goal of the maven-scala-plugin
when triggering Maven from the command line but this goal is not triggered in Eclipse and the resources are not created).
ISPN-5040 Upgrade to JGroups 3.6.1.
- Drop DISCARD2
- Use resend_last_seqno="true" in NAKACK2
ISPN-3938 AdvancedAsyncCacheLoader.process() concurrency issues

Simplify ExecutorAllCompletionService to track the tasks itself instead of
using an ExecutorCompletionService.