Added downloading of textures when clicking on a menu item

For this I made the operator a state machine; when its state is set to
'QUIT' it'll quit. Different states can have different OpenGL drawing
functions.

For now, to help development, the state is drawn in the bottom left corner.

blender_cloud/__init__.py

@@ -45,7 +45,7 @@ else:
 import logging
 
 import bpy
-from bpy.types import AddonPreferences, Operator, WindowManager
+from bpy.types import AddonPreferences, Operator, WindowManager, Scene
 from bpy.props import StringProperty
 
 
@@ -147,7 +147,12 @@ def register():
         name="Blender Cloud node UUID",
         default='')  # empty == top-level of project
 
-    logging.basicConfig(level=logging.INFO,
+    Scene.blender_cloud_dir = StringProperty(
+        name='Blender Cloud texture storage directory',
+        subtype='DIR_PATH',
+        default='//textures')
+
+    logging.basicConfig(level=logging.DEBUG,
                         format='%(asctime)-15s %(levelname)8s %(name)s %(message)s')
     async_loop.setup_asyncio_executor()
     gui.register()