Missing ability to set parameterMappings via the add_widget function

[dhopp1]

Currently there is no ability to set the parameterMappings field when adding a widget to a dashboard (i.e. setting whether the parameter is a dashboard or widget-level parameter) with the add_widget function. I would propose the attached changes to the function to add that capability.
add_widget.txt

[damienzeng73]

PR's welcome.