Negative triangularity grid generation

[holm10]

• Search algorithm in PFR has 3 options
  • X-point vertically up/down, towards HFS
  • For negative triangularity PFR is more towards LFS
• Could consolidate wedge limiter documentation and improvements

Possible solution is to add one more option of altsearch == 3 to allow to search diagnoally out from the X-pt

[holm10]

Menglong to commit changes to NT grid generation to separate branch