Raise a proper error message if the filename for SaveAs does contain the .rtd extension

#### Description:

When using the `SaveAs` command with an `Exectute` component - if the filename does contain the .rtd extension is produces the following error:

> 1. This component failed to run properly.
> - Error: Error HRESULT E_FAIL has been returned from a call to a COM component.
> - Occured in BH.Adapter.Robot.RobotAdapter.RunCommand(SaveAs command)
> called from BH.Adapter.Robot.RobotAdapter.Execute(IExecuteCommand command, ActionConfig actionConfig)
> - Are you sure you have the correct type of inputs? Check their description for more details.

#### Steps to reproduce:

See above.

#### Expected behaviour:

The adapter should raise an error instructing the user to provide a filepath with the correct extension.

#### Test file(s):