move to tools methods for working with manual booleans #3709

Also fixed a bug adding boolean when pset is already added and representation type in add_boolean

```
  File "\addons\blenderbim\tool\ifc.py", line 201, in execute
    IfcStore.execute_ifc_operator(self, context)
  File "\addons\blenderbim\bim\ifc.py", line 336, in execute_ifc_operator
    result = getattr(operator, "_execute")(context)
  File "\addons\blenderbim\bim\module\model\opening.py", line 534, in _execute
    data = json.loads(pset["Data"])
  File "\addons\blenderbim\libs\site\packages\ifcopenshell\entity_instance.py", line 248, in __getitem__
    if key < 0 or key >= len(self):
TypeError: '<' not supported between instances of 'str' and 'int'
```

src/ifcopenshell-python/ifcopenshell/api/geometry/add_boolean.py

@@ -57,9 +57,11 @@ class Usecase:
                 )
             ):
                 items.append(self.file.createIfcBooleanClippingResult(self.settings["operator"], item, result))
+                representation_type = "Clipping"
             else:
                 items.append(self.file.createIfcBooleanResult(self.settings["operator"], item, result))
-        self.settings["representation"].RepresentationType = "CSG"
+                representation_type = "CSG"
+        self.settings["representation"].RepresentationType = representation_type
         self.settings["representation"].Items = items
         return items