[Ownership] Allow object composition based on role

Supports resolution of nasa/mct#255 by allowing object composition when the owner of an object is a role, as provided/recognized by installed role service(s). 

Role service which addresses the specific use case which motivates nasa/mct#255 is under development on branch https://github.com/VWoeltjen/MCT-Plugins/tree/mct255 and depends upon this change.

```
 Wrote or re-wrote unit tests (Y/N): Y
 Ran entire suite of unit tests successfully (Y/N): Y
 Verified bug fix with the described replication steps or verified the implementation meets the requirement cited (Y/N): Yes (partial; solution to underlying use case depends on external plug-in)
 Code coverage requirements satisfied (new code=80%, changed code=at least as high as existing) (Y/N): Y
 Code review date and attendees: Self-review by pull request
 Describe potential impact on other areas of the code: Composition policy (triggered by drag drop, create menu, other object composition tasks)
 Describe any test prerequisites for this fix (e.g., restart the database): Run with a plugin that provides a Role Service (e.g. scenario from nasa/MCT-Plugins)
 For bugs marked "Regression - Yes", describe the cause of the regression: N
 Did you modify any pom.xml file? If yes, did you thoroughly document your changes and reasons? N
```