launch
Launches the session preparations. This includes copying needed files to temporary folder and other operations.
This method allows to re-launch the session when it's not in process of preparations and session's state hasn't reached Awaiting yet, e.g. when preparations were interrupted with process death.
In general, this method should not be used directly, use addStateListener with TerminalStateListener or await() instead.
Return
true if session preparations have been launched due to this invocation. false if session preparations are in progress or have been already done, or session was cancelled.