This change adds a deprecated field to the API token web API resource. This

is a bool showing whether the token was generated by a deprecated token

generator. We also now display a notice on the API tokens config page if a

token is deprecated. The notice encourages the user to delete the deprecated

token and generate a new one.

Made some GET requests to the /api-tokens/ list endpoint and saw that the

deprecated field was included in the token resources.
Created some deprecated tokens and made sure they behave correctly and

  appear with the notice in the API tokens page.
Ran JS unit tests.
Ran reviewboard/webapi/tests/test_api_token.py