First attempt at ripping out agnostic code into ifcopenshell.api namespace. See #1399.

src/ifcopenshell-python/ifcopenshell/api/pset_template/add_pset_template.py

@@ -0,0 +1,17 @@
+import ifcopenshell
+
+
+class Usecase:
+    def __init__(self, file, settings={}):
+        self.file = file
+        self.settings = {}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        self.file.create_entity("IfcPropertySetTemplate", **{
+            "GlobalId": ifcopenshell.guid.new(),
+            "Name": "New_Pset",
+            "TemplateType": "PSET_TYPEDRIVENONLY",
+            "ApplicableEntity": "IfcTypeObject"
+        })