Fix example code.
Remember floater rectangle
Add AIMeshUpload and fix LLMeshUploadThread

* Removes polling stuff (call to gMeshRepo.update()) which did
  nothing but check if uploads already finished.
* Just creates and runs the state machine (AIMeshUpload) instead
  of creating an LLThread derived class (LLMeshUploadThread) and
  adding that to a queue, then have the main thread start it
  after adding it to another queue in order to keep track of
  the instances (both queues are gone).
* mWholeModelUploadURL was moved to the state machine, because
  it needs a life time till the responders finishes (can't be
  part of the thread object).
* LLMeshUploadThread is now derived from AIThreadImpl instead
  of LLThread, so it can be run in a state machine thread.
* The call to LLHTTPClient::post is now done from the main
  thread instead of from the thread, but I don't think that is
  a problem.