Read the data type for #vertices/face from PLY header

[cy94]

• The loadFromPLY function assumes the PLY header line about faces to be property list uchar int vertex_indices.
• However, the uchar field could be replaced by int, for example in the output of Poisson Reconstruction's Surface Trimmer.
• Hence, read this line of the header and store the number of bytes in verticesPerFace in the PlyHeader
• Then use it to correctly read the faces in the PLY file.
• Example data to test this code: test.zip
  • Earlier behaviour: throws a vector index out of bound exception
  • Now: file is read successfully
• Additionally remove some commented code