Add new members to a club as admin or president

[bfbachmann]

When I'm signed in as the admin or president of a club, I should be able to add new members by full name or username.

[bfbachmann]

You'll need to add a method to api.js that does a query like this
http://localhost:8080/users/search?username=bfbachmann&full_name=bfbachmann

[bfbachmann]

Example: