Issues with imported presentation ids

When an existing presentation/qml-stream is imported, it would be possible to check the original id from the original project and use that instead of default it. Default id can be used in case of duplicate id.

When a presentation is imported as a subpresentation asset of another presentation, then the original id is preserved. However, it should be checked how duplicate ids are handled in this case - import should never result in duplicate ids. Import can get bit complicated if duplicate ids are detected in this case, because changing the ids means imported parent presentation needs to be updated to look for the new ids.