Changed AccountManager to only rely on a proper OAuth response.
This involved making another request after the initial OAuth authorization.
Because of this now-two-step process, some methods and signals were renamed
to make their purpose more clear. Additionally, a _hasProfile member variable
was added to DataServerAccountInfo in order to allow for knowledge of whether
the profile elements had been fetched when being deserialized from disk.
Error handling for the whole process is still nonexistant.
Now determines hasProfile from presence of username
Totally removed DataServerAccountInfo's JSON constructor
Merge pull request #3022 from jmgrosen/19780

Code Review for Job #19780
Merge branch 'master' of https://github.com/highfidelity/hifi into OculusOverlay