Sort approved users by their application date

[talavis]

Describe the pull request:

• [ ] Bug fix
• [ ] Functional change
• [ ] New feature
• [ ] Code cleanup
• [ ] Build system change
• [ ] Documentation change
• [ ] Language translation

Pull request long description:

As the response from postgres is unsorted, sort users by application date before displaying them in the admin interface.

Related issues:

Fixes #585.