Added IfcZone to systems UI in IFC2X3 #3905

In IFC2X3 IfcZone is a subtype of IfcGroup but not subtype of IfcSystem (it become one after IFC4), therefore IfcZone wasn't presented anywhere in BBIM UI.
It's a bit confusing though to include IfcZone in systems when it's not actually a IfcSystem but having it in IfcGroups would be confusing too.

src/blenderbim/blenderbim/bim/module/system/data.py

@@ -47,6 +47,9 @@ class SystemData:
         declaration = tool.Ifc.schema().declaration_by_name("IfcSystem")
         declarations = ifcopenshell.util.schema.get_subtypes(declaration)
         version = tool.Ifc.get_schema()
+        if version == "IFC2X3":
+            declarations += [tool.Ifc.schema().declaration_by_name("IfcZone")]
+
         # We're only interested in systems for services. Not sure why IFC groups these together.
         return [
             (c, c, get_entity_doc(version, c).get("description", ""))
@@ -56,7 +59,7 @@ class SystemData:
 
     @classmethod
     def total_systems(cls):
-        return len(tool.Ifc.get().by_type("IfcSystem"))
+        return len(tool.System.get_systems())
 
 
 class ObjectSystemData:
@@ -85,7 +88,7 @@ class ObjectSystemData:
 
     @classmethod
     def total_systems(cls):
-        return len(tool.Ifc.get().by_type("IfcSystem"))
+        return len(tool.System.get_systems())
 
     @classmethod
     def connected_elements(cls):

src/blenderbim/blenderbim/tool/system.py

@@ -127,11 +127,17 @@ class System(blenderbim.core.tool.System):
         props.system_attributes.clear()
         blenderbim.bim.helper.import_attributes2(system, props.system_attributes)
 
+    @classmethod
+    def get_systems(cls):
+        if tool.Ifc.get_schema() == "IFC2X3":
+            return tool.Ifc.get().by_type("IfcSystem") + tool.Ifc.get().by_type("IfcZone")
+        return tool.Ifc.get().by_type("IfcSystem")
+
     @classmethod
     def import_systems(cls):
         props = bpy.context.scene.BIMSystemProperties
         props.systems.clear()
-        for system in tool.Ifc.get().by_type("IfcSystem"):
+        for system in cls.get_systems():
             if system.is_a() in ["IfcStructuralAnalysisModel"]:
                 continue
             new = props.systems.add()