Improve Project Creation/Editing with large user base

When editing a project in Crucible, it will basically load every user in the system and add it to the HTML so that it can populate the Users fields. If you look at the source of this page once it has loaded there will be elements for each user. When you have many users (20,000+) this page can sometimes never load.

We should update this page to use the Ajax-style selector that's used in the rest of the system so that we don't have to retrieve the entire user list when building the page source.