New system module with UI to browse systems in an IFC.

src/ifcopenshell-python/ifcopenshell/api/system/remove_system.py

@@ -0,0 +1,11 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"system": None}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        for rel in self.settings["system"].IsGroupedBy or []:
+            self.file.remove(rel)
+        self.file.remove(self.settings["system"])