implement annotation for allowing higher tier configuration without forcing library loading

[cokieffebah]

Use Case

Allow a tier to define a configuration but not force the library to be loaded by subsequent project

Feature Request

implement '@transient' annotation in pipeline_config such that during configuration aggregration if the affected item is not redefined, the final configuration annotation does not contain the annotated configuration.

the @transient would have to be redefined on each intermediate tier ... the annotation would not automatically cascade through an intermediate tier(s) to the final projects

tier 1 pipeline_config.groovy

...
libraries{
  @transient maven{
      base_command = "mvn"
   }
  ...
}

project1 pipeline_config.groovy

// no libraries.maven
libraries{

}

project2 pipeline_config.groovy

libraries{
  maven{}
}

then the project1 final configuration will not contain libraries.maven and project 2 will have libraries.maven with the base_command