Pyinstaller support (#93)

* Add main.spec

* Fix issue where fetching supported extensions would crash with no default installation

src/engines/blender/blender_ui.py

@@ -1,9 +1,9 @@
 
 class BlenderUI:
     @staticmethod
-    def get_options(instance):
+    def get_options(system_info):
         options = [
-            {'name': 'engine', 'options': instance.supported_render_engines()},
+            {'name': 'engine', 'options': system_info.get('engines', [])},
             {'name': 'render_device', 'options': ['Any', 'GPU', 'CPU']},
         ]
         return options