Changing nchunk_points back to nchunk.points

I submitted the last commit after checking my `cam_chunk` file against the `chunk` file in Alain's repo to make sure I hadn't introduced any errors.
When I saw that his code had `nchunk_points` I assumed that my change was a mistake, and I reverted it.

However, upon closer inspection of the code, I believe that it should, in fact, be changed.
There is no reference to `nchunk_points` elsewhere in the code, though there is a similarly named `chunk_points` variable.
`nchunk` is an instance of `camPathChunkBuilder` which has `points`, but not `nchunk_points`.