Navmesh Improvements

[zach2good]

I affirm:

• [x] that I agree to Project Topaz's Limited Contributor License Agreement, as written on this date
• [x] that I've tested my code since the last commit in the PR, and will test after any later commits

Huge props to @xenonsmurf for doing 99% of the legwork for this, I just asked him nicely to do stuff and then tidied up the code and tested it.

To update your submodule (the navmeshes) run: git submodule update

EDIT: Code changes have been moved to here: https://github.com/project-topaz/topaz/pull/1458 This PR will become only navmesh submodule changes 👍

[TeoTwawki]

sounds like you two at least partially solved #182