API: Allow creation of more than one user token

[agjohnson]

Right now, the API token view only looks like a many to many sort of relationship. Instead, it's only possible to make a single API token and then the create button is disabled. Eventually, we probably want to make this UI a true many to many relationship, like other services where multiple API tokens are possible.

[agjohnson]

Note, we are currently working on adding more API tokens for users/projects with the build API token change. This could eventually change the API token UI for the user, but is not changing anything at the moment.

I'm going to transfer this off the theme, as it's mostly settled here, and we need the underlying API token change in the application first. It's not clear how much of a priority this is though.