Changed fbx exporter to allow for arbitrary custom properties

Fixes #356 . But needs testing.

This should also allow users to set the highlighttype for highlight empties as described in #336 .

space-engineers-utilities/export/seut_custom_fbx_exporter.py

@@ -152,15 +152,9 @@ def fbx_data_object_elements(root, ob_obj, scene_data):
     
     """
     if obj_type == b"Empty":
-        se_custom_property_file = ob_obj.bdata.get('file', None)
-        se_custom_property_highlight = ob_obj.bdata.get('highlight', None)
-
-        if se_custom_property_file is not None:
-            _fbx.elem_props_template_set(tmpl, props, "p_string", b"file", str(se_custom_property_file))
-
-        if se_custom_property_highlight is not None:
-            # HARAG: TODO SE supports mutliple highlight shapes via <objectSPECIFICATION1>;<objectSPECIFICATION2>;...
-            _fbx.elem_props_template_set(tmpl, props, "p_string", b"highlight", str(se_custom_property_highlight))
+        for key in ob_obj.bdata.keys():
+            if key not in '_RNA_UI' and key != 'seut':
+                _fbx.elem_props_template_set(tmpl, props, "p_string", bytes(key, 'utf-8'), str(ob_obj.bdata.get(key, None)))
 
     if obj_type == b"Mesh" and ob_obj.bdata.rigid_body:
         rbo = ob_obj.bdata.rigid_body