FCSV files created in recent 3D Slicer versions are not properly parsed

[rg2]

The default behavior of recent 3D Slicer versions (e.g. 4.11.x) is to write FCSV files with points already in LPS coordinates. The xReg parsing code assumes RAS coordinates, consistent with FCSV files saved from Slicer 4.10.

Modifications should be made that check the file version and coordinate system strings.

[rg2]

PR #14 adds correct support for reading FCSV files created using 3D Slicer 4.11.x and 5.x.