Mark a front side of point entities

[Qwertyus3D]

(Especially, but not only because) while there is no support of loading models for point entities, it could be very useful to mark somehow a front side of point entities to show how entities are oriented in space (at least, selected ones). So we can easily check a monster's gaze direction etc. It could be an additional arrow, or specific color of front side or its' wireframe.

[UnrealKaraulov]

@Qwertyus3D

I do it in my bspguy fork :

https://github.com/UnrealKaraulov/newbspguy