Allow passing parameters from embedding Webpage into Widgets

[graphcon]

Please allow passing parameters from the surrounding Webpage into Widgets. This means, if you embed a workspace as IFrame, you can add additional parameters. E.g. currently <iframe src="<url_to_workspace>?mode=embedded"...> may be extended <iframe src="<url_to_workspace>?mode=embedded&user_id=1"...>

The given parameter user_id is then passed to, for example, an operator which accepts a specific parameter as input.

Currently this is prevented as the operator's URLs do not include such GET parameters.