Geodesics across shared boundaries

[medakk]

Figure out how to do geodesics across multiple meshes that have a shared boundary.

[sheryjoe]

This is to enable geodesic samples for shared boundaries. Given two particles, one particle on domain A and another on domain B, we want to get the geodesic distance between them which is the length of the shortest path from particle A to particle B passing through the shared boundary.

this will need:

• given particle A and the shared boundary, we want an API that computes the goedesic distance to the contour and also results the closest point C to that contour (from which the geodesic distance was computed).
• compute geodesic from C (on the shared boundary) to particle A
• adding these two distances will give the geo distance from A to B.

[iyerkrithika21]

@akenmorris can we move this to the next release?