Consolidate point mesh forward kernels

Summary: This diff creates the generic MeshForwardKernel which can handle distance calculations between point, edge and faces in either direction. Replaces only point_mesh_face code for now.

Reviewed By: gkioxari

Differential Revision: D24543316

fbshipit-source-id: 302707d7cec2d77a899738adf40481035c240da8

Author: theschnitz