CookieAuthenticate: Implementation error

- Update the CookieAuthenticate class from upstream
- AutoLoginComponent was doing all the work instead of reusing
  CookieAuthenticate. Fix it by removing those and move cookie
  verification into the Authenticate class.
- Use hash_hmac() against cookie payload
Don't respond when data is coming from login request

Skip processing when request contains POSTed data.
Closes: #412
Merge branch '1.5-autologin'