Minor documentation clarifications

[oleg-alexandrov]

Dear texrecon developers,

I find your tool very useful. Thank you! I use it with a flying robot that collects depth clouds, fuses them, and textures the combined cloud with images it acquires with a separate camera. Hence the depth cloud does not come from the same modality as the textures, but your tool does great.

Here is a tiny pull request, basically clarifying some things. As future work, I plan to expose to the user the outlier factor value and the maximum angle from a ray hitting a face and the face normal (those are now hard-coded to 6e-3 and 75 degrees), and also the maximum ray length (which now is not restricted but could be an option to avoid very far views) but that is for another time.