title: Salesforce SOAP SessionId as REST token
body: <p>I'm logging my users in using SOAP in my app. But then I want to use Analytics API, which is REST. But I don't want them to enter their credentials all over again. 
  Is there a way that I can use my already obtained SOAP sessionId as the token for REST API?
  When I tried to do that, I got an authentication error back from the REST call. Did I miss something or is it just not possible?</p>