Implement arithmetic formulas for cost value components

src/ifcopenshell-python/ifcopenshell/api/cost/edit_cost_value.py

@@ -0,0 +1,13 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"cost_value": None, "attributes": {}}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        for name, value in self.settings["attributes"].items():
+            if name == "AppliedValue" and value is not None:
+                # TODO: support all applied value select types
+                value = self.file.createIfcReal(value)
+            setattr(self.settings["cost_value"], name, value)