WIP port classification module with new features. See #1222.

* Adaptive UI based on IFC version
 * You can now load new classification libraries on the fly
 * You can mix classification libraries with project references

src/ifcblenderexport/blenderbim/bim/module/classification/edit_classification.py

@@ -0,0 +1,13 @@
+class Usecase:
+    def __init__(self, file, settings=None):
+        self.file = file
+        self.settings = {
+            "classification": None,
+            "attributes": {}
+        }
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        for name, value in self.settings["attributes"].items():
+            setattr(self.settings["classification"], name, value)