Add recipe to extract only spaces (#1521)

`ExtractElements` was not allowing to extract only spaces.
It also helps to workaround revit-ifc failure in linking spaces.
See: https://github.com/Autodesk/revit-ifc/issues/15

src/ifcpatch/ifcpatch/recipes/ExtractSpaces.py

@@ -0,0 +1,29 @@
+import ifcopenshell
+import ifcopenshell.util.selector
+
+
+class Patcher:
+    def __init__(self, src, file, logger, args=None):
+        self.src = src
+        self.file = file
+        self.logger = logger
+        self.args = args
+
+    def patch(self):
+        self.contained_ins = {}
+        self.aggregates = {}
+        self.new = ifcopenshell.file(schema=self.file.wrapped_data.schema)
+        self.owner_history = None
+        for owner_history in self.file.by_type("IfcOwnerHistory"):
+            self.owner_history = self.new.add(owner_history)
+            break
+        selector = ifcopenshell.util.selector.Selector()
+        for space in selector.parse(self.file, ".IfcSpace"):
+            self.add_element(space)
+        self.file = self.new
+
+    def add_element(self, element):
+        self.new.add(element)
+        for rel_aggregate in element.Decomposes:
+            self.add_element(rel_aggregate.RelatingObject)
+            self.new.add(rel_aggregate)