Begin low-level API for Image v1 and v2

image list for v1 and v2:
* Add --public|--private to command parsers
* Implement local public/private filtering for v1 image_list()
* Pass public/private filter to server for v2 image_list()

Change-Id: Ie7c24ea2d1bf2b3b1b7fa342eb45fee45894634d

doc/source/command-objects/image.rst

@@ -139,12 +139,21 @@ List available images
 
     os image list
         [--page-size <size>]
+        [--public|--private]
         [--long]
 
 .. option:: --page-size <size>
 
     Number of images to request in each paginated request
 
+.. option:: --public
+
+    List only public images
+
+.. option:: --private
+
+    List only private images
+
 .. option:: --long
 
     List additional fields in output