[Info View] Support custom visual controls

This adds support for plugin-provided GUI elements in the Info View for property-editing, nasa/mct#192. Previously Info View only supported only a finite set of standard GUI components ("visual controls") for editing properties of an object in the Info View.

 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): Y
 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 (no other developers available)
 Describe potential impact on other areas of the code: info View
 Describe any test prerequisites for this fix (e.g., restart the database): Use of plug-in which utilizes this feature (should be supported in Scenario plugin after resolution of nasa/MCT-Plugins#39)
 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