Creates a result from the specified resultText by extracting the result mode from the text and delegating to a corresponding IResultFactory, if any.
This method guarantees that the return value will always be non-null.
resultText must always be of the form
"<resultmode>:<textual result representation>". The
resultmode will be extracted and the corresponding IResultFactory (previously registered using RegisterResultMode) is called to actually create the IResult instance. If no factory matches
resultmode, the call is handled to the DefaultResultFactory.
|ArgumentNullException||if either resultText is null or CreateResult returned null.|