Revisit what default behavior for ProjectContact GetList should be

The GetList behavior for ProjectContact has been changed such that it only returns Contacts and breaks the infinite-scrolling feature. This was an attempt to deal with the high-chance of duplicate contact results when using the api to display contacts whom are associated with volunteer projects.

That this is reasonable behaviour is defensible, because the other potential use-cases are of questionable use. That is:

• Display a list of Project-Contacts (requires concatenating the two entity labels)
• Display a list of Projects: you would use Project, not Project-Contact

One possible improvement would be to display contacts without the dedupe (and enable the infinite-scroll) only when the search field of select2 is disabled. If a search input is displayed to the user.

More discussion: https://github.com/GinkgoFJG/org.civicrm.volunteer/pull/14