Export Obj TAGs

Add a TAG string property to entity.

The scope of TAG is  an additional information added as a suffix to the name of mesh in obj file structure.

Example

Actualy in the structure of obj file any mesh are specify by

g Object_XXX where XXX is a progressive integer and corresponds to an Eyeshot entity (e), be it a mesh or a solid.

if i have a Tag i can specify

e.Tag="WALL"

and in obj I find  g Object_0_WALL.

In this way I can easily identify all the parts, or add other useful information if I use the obj file as an interchange medium for other software.