Karaf4 features and distribution

Karaf4 features and distribution

+ upstream-artifact split to multiple files depending on type.
+ Version properties moved to a parent pom separate from aggregators.
+ Added TODOs to remind only atrifact-artifacts should be referred to ideally.
+ distribution-artifact still contains all types in one file.
+ Karaf 4 features added, both distribution and some upstream.
+ features/ split to singles/ and repos/.
+ odl-restconf and odl-netconf-mdsal are the only upstream Karaf 4 features (compatible).
+ Additionaly features4-netconf-connector added (user-facing features are incompatible).
+ features3-distribution as artifactId for the Karaf 3 distribution feature repo.
*+ Karaf 4 feature repos do not contain "integration" in artifactId.
*+ So othe Karaf 3 feature repos kept their artifactId, no releng change needed.
- The generated features-index descriptor lists single features (very ugly).
+ Karaf 3 related directories contain "3", Karaf 4 ones do not contain number.
*- Except distribution-karaf to not confuse releng, it will be deleted soon anyway.
+ distribution:karaf is the artifact creating Karaf 4 distribution.
*+ New content for org.ops4j.pax.url.mvn.cfg with minimal changes (to work offline) from default.
*- Other resources duplicated without any change.
*- aaa-cli-jar had to be commented out for the build to succeed.
+ ${project.*} used whenever possible (except in parent poms of course).
+ Modules named "all" listed last in aggregator (as if the order mattered).
+ Descriptions and comments improved.
+ Pom <project> atributes in separate lines.
+ Some copypastas from previous Changes fixed.

Change-Id: Ifed7d811e4f049e90f4a8cfa759ab2f67ae51f5b
Signed-off-by: Vratko Polak <vratko.polak@gmail.com>