Bugfix: ToSTEP call added

[samil-akhmedov]

BACKGROUND:

• Writing model data to the memory stream doesn't work correctly (model.ToIFC) as it lacks the ToSTEP method call.
• Not leaving the underlying stream open while writing model data to the memory stream prohibits the subsequent calls for that stream.

DESCRIPTION:

• The ToSTEP method call was added to the ToIFC method.
• leaveOpen: true parameter was added to the StreamWriter instance inside the ToIFC method.

TESTING:

• Write any model data into MemoryStream instance.

FUTURE WORK:

• No further work is required.

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This change is