Specify OAuth profile for SciTokens

[jbasney]

Document OAuth flows for obtaining SciTokens per RFC 6749.
Show example requests/responses similar to the examples in the RFC for Obtaining Authorization, Issuing an Access Token, Refreshing an Access Token, and Accessing Protected Resources.

I expect the Access Token Response example to include a self-encoded access token and refresh token similar to:

 HTTP/1.1 200 OK
 Content-Type: application/json;charset=UTF-8
 Cache-Control: no-store
 Pragma: no-cache

 {
   "access_token":"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOjEwMDAsImlzcyI6Imh0dHBzOi8vYXV0aG9yaXphdGlvbi1zZXJ2ZXIuY29tIiwiYXVkIjoiaHR0cHM6Ly9leGFtcGxlLWFwcC5jb20iLCJpYXQiOjE0NzAwMDI3MDMsImV4cCI6MTQ3MDAwOTkwMywic2NvcGUiOiJyZWFkIHdyaXRlIn0.zhVmPMfS3_Ty4qUl5ZMh4TipXsUCSH0mHzb4P_Ijhxs",
   "token_type":"Bearer",
   "expires_in":7200,
   "refresh_token":"tGzv3JOkF0XG5Qx2TlKWIA",
 }