Add Project Relationship Defaults to Defaults UI

Project Relationships should be included in our new Project Default Settings UI.
This would mean adding support in BAO::Project::composeDefaultSettingsArray
as well as Form/Defauls.php

This enhancement should support all Volunteer Relationship types
This enhancement should support tokens such as [self] and [employer] that are based on relationships for the person/contact creating a new Volunteer Project.

The implementation of this feature should be such that if the user (admin) takes no action to set their own defaults, it replicates what is currently in ProjectUtil::getSupportingData