Nav Editmodes Preview

[Dadido3]

Looks good, it's really helpful and non intrusive while creating nav meshes.

A few points that could be improved:

• The "reposition node" mode can be used to move a node along a single axis per right click. An additional preview that shows the result of a repositioning along the single axis (main looking direction) would be useful.
• The preview for "copy nodes" seems to be larger than the result, also it doesn't show the correct preview when you want to do a copy along the vertical axis.

It's up to you if you want to improve the "reposition node" preview, but i'll wait until you supply a fix for the "copy nodes" mode, as this seems to be done quickly. Just push an update to your delstre/D3bot repository, and once the preview works correctly, i'll merge this request.

Thanks very much for the contribution, it really improves the edit modes' ease of use.

[Dadido3]

I fixed some stuff, and remove the use of table.HasValue as this scales really badly when there are a lot of nodes/items.

Again, thanks very much for the contribution