Cimpli 1.2.0 (GMS2)

• implemented the Providers system for resolving requested values (dependencies)
• added the init method to TaskProcessor/CimpliTaskProcessor types, as well as a corresponding method and task_started event to Task/CimpliTask implementation; CimpliWorker executes the initialisation upon creation
• added the cleanup method to TaskProcessor/CimpliTaskProcessor types, and added calling it upon the CimpliTask finishing/cancellation
• renamed is_cancelled/task_cancelled to is_canceled/task_canceled in the Task interface to consistently use American spelling for member names
  • the "canceled" spelling has a precedent in .NET Framework, e.g. in TaskStatus enum
  • at the same time, the "cancellation" spelling should remain, also having the .NET Framework precedent in CancellationToken struct