Small Refactor to Bimtester + Diff Module (#1271)

* Refactoring of BIMTester Module

* Modification to Bimtester refactor + Diff refactor

Co-authored-by: Ihab El Aghoury <ihab_elaghoury@yahoo.ca>
Co-authored-by: Dion Moult <dion@thinkmoult.com>

src/ifcblenderexport/blenderbim/bim/module/diff/prop.py

@@ -0,0 +1,21 @@
+import bpy
+from blenderbim.bim.prop import StrProperty
+from bpy.types import PropertyGroup
+from bpy.props import (
+    PointerProperty,
+    StringProperty,
+    EnumProperty,
+    BoolProperty,
+    IntProperty,
+    FloatProperty,
+    FloatVectorProperty,
+    CollectionProperty,
+)
+
+
+class DiffProperties(PropertyGroup):
+    diff_json_file: StringProperty(default="", name="Diff JSON File")
+    diff_old_file: StringProperty(default="", name="Diff Old IFC File")
+    diff_new_file: StringProperty(default="", name="Diff New IFC File")
+    diff_relationships: StringProperty(default="", name="Diff Relationships")
+