Initial Flamenco support.

Lots to do:

- Doesn't call BAM yet to copy files onto the job storage folder (even
  though you can configure that folder).
- Uses the same project as Attract, so you have to select it in an
  unintuitive location. Also, you can only start Flamenco jobs on a project
  that is Attract-enabled (and not necessarily Flamenco-enabled).

blender_cloud/utils.py

@@ -62,3 +62,41 @@ def find_in_path(path: pathlib.Path, filename: str) -> pathlib.Path:
                 return subpath
 
     return None
+
+
+def pyside_cache(propname):
+    """Decorator, stores the result of the decorated callable in Python-managed memory.
+
+    This is to work around the warning at
+    https://www.blender.org/api/blender_python_api_master/bpy.props.html#bpy.props.EnumProperty
+    """
+
+    if callable(propname):
+        raise TypeError('Usage: pyside_cache("property_name")')
+
+    def decorator(wrapped):
+        """Stores the result of the callable in Python-managed memory.
+
+        This is to work around the warning at
+        https://www.blender.org/api/blender_python_api_master/bpy.props.html#bpy.props.EnumProperty
+        """
+
+        import functools
+
+        @functools.wraps(wrapped)
+        # We can't use (*args, **kwargs), because EnumProperty explicitly checks
+        # for the number of fixed positional arguments.
+        def wrapper(self, context):
+            result = None
+            try:
+                result = wrapped(self, context)
+                return result
+            finally:
+                rna_type, rna_info = getattr(self.bl_rna, propname)
+                rna_info['_cached_result'] = result
+        return wrapper
+    return decorator
+
+
+def redraw(self, context):
+    context.area.tag_redraw()