Yet another CLIng cleanup.
Changes:
* pull out Executor, it does not belong to CLIng (new maven-executor module created with no deps)
* resident and maven invoker fixes (proper handling of resources now), no more SO/OOMs
* enabled UTs in maven-cli (that revealed the issues)
* small bug fixes discovered in cli, improved executor to reveal maven version
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https://issues.apache.org/jira/browse/MNG-8386
Tamas Cservenak