read gocad

[millerta]

Occasionally a gocad file can have 0-based numbering for VRTX's.
LaGriT will read and pass this 0 ID to written AVS files, but these files will crash lagrit and paraview.

Add a warning at least,
But need to change to 1-based numbering

Example 0-based file written by JewelSuite:

/project/meshing/SEISMIC/LYNM/gfm_ptunnel_pe1/JS_gocad_blocks
GOCAD TSurf 1
HEADER {
name:LWT
*solid*color:0.645379 0.268908 0.258824 0.5
*mesh:false
}
GOCAD_ORIGINAL_COORDINATE_SYSTEM
NAME from_XYZ
AXIS_NAME "U" "V" "W"
AXIS_UNIT "m" "m" "m"
ZPOSITIVE Depth
END_ORIGINAL_COORDINATE_SYSTEM
GEOLOGICAL_TYPE unconformity
TFACE
VRTX 0 573429 4119945 -1556.079
VRTX 1 573429 4120115 -1576.0642
VRTX 2 574169 4119945 -1460.7174