Introducing a Detour NavMesh creator helper library

This new library facilitates the creation of navmeshes for Detour. At the moment it only supports the creation of Tiled NavMesh where all tiles uses the same configuration.

It is now used by `DetourCrowdTest` and `DetourCrowdDemo`. The goal is to also use it in `RecastDemo` to unify all navmesh creation helpers and hopefully facilitate first contacts with Recast/Detour.

**Further improvements**
- The file format used by `DetourCrowdDemo` now allows the sharing of behaviors between agents.
- A new `DetourCrowdDemo` sample now showcases the avoidance of non-moving agents.
- In files otherwise modified, existing *space* indents have been changed to *tab* indents.