Make "hitObjectId" numerical

[han16nah]

Problem description

Currently, we cannot really use the hitObjectId point cloud parameter when processing the simulation output with pyhelios, because it is not numerical and therefore not written to the output array (when running outputToNumpy(), see output_handling.py#L37

Solution

I would prefer hitObjectId to be numerical. If not setting a custom scenepart ID, the hitObjectID is a unique, incremental ID anyways. However, the id tag of the <part> XML tag currently allows setting a string as scenepart ID.

So we could:

• [ ] adjust the variable type in the HELIOS++ core
• [ ] uncomment the respective line in output_handling.py#L37
• [ ] change the data type in the scene XSD:

<xs:attribute type="xs:int" name="id" use="optional"/>