PointsAlgo::mergePoints loses interpretation

[ericmehl]

Version: Cortex 10.3.0.0-release
3rd-party modules: None

Description

It looks like PointsAlgo::mergePoints does not copy the geometric interpretation when merging point primitives.

Steps to Reproduce

1. Create a few PointsPrimitive objects with vertex data that has an interpretation other than Numeric.
2. Merge them using mergePoints()
3. Check the output interpretation.
4. The interpretation reverts to Numeric.

I think it could be fixed by setting the interpretation after this line?

cortex/src/IECoreScene/PointsAlgo.cpp

Line 170 in 4528f3a

container = new T();

Though there may also be some more to do or at least documentation about what happens for conflicting interpretations.