Feature Request: 'Bridge' and 'Teleporter' on mesh

[afpro]

• Bridge
  Multilayer navmesh is really useful.
• Teleporter
  Unity3d 'NavMeshLink' alternative.

[mockersf]

I have layers working in #58, I want to do a bit of cleanup before merging but it should be almost good to go

Teleporters are next on the list of things I want to implement 👍