Support for version and extension discovery

- Supports unauthenticated call to Keystone to discover
  supported API versions
- Added command-line support (usage: keystone discover)
- Added client support (keystoneclient.genenric client).
  Client returns dicts, whereas shell command prints
  formated output.
- Added tests for genenric client
- Replicates 'nove discover' in python-novaclient
- Starts to address blueprint keystone-client
- keystone discover output looks like this:
    $ keystone discover
    Keystone found at http://localhost:35357
        - supports version v1.0 (DEPRECATED) here http://localhost:35357/v1.0
        - supports version v1.1 (CURRENT) here http://localhost:35357/v1.1
        - supports version v2.0 (BETA) here http://localhost:35357/v2.0
            - and HP-IDM: HP Token Validation Extension
            - and OS-KSADM: Openstack Keystone Admin
            - and OS-KSCATALOG: Openstack Keystone Catalog

Change-Id: Id16d34dac094c780d36afb3e31c98c318b6071ac

keystoneclient/utils.py

@@ -67,3 +67,24 @@ def find_resource(manager, name_or_id):
         msg = "No %s with a name or ID of '%s' exists." % \
               (manager.resource_class.__name__.lower(), name_or_id)
         raise exceptions.CommandError(msg)
+
+
+def unauthenticated(f):
+    """ Adds 'unauthenticated' attribute to decorated function.
+
+    Usage:
+        @unauthenticated
+        def mymethod(f):
+            ...
+    """
+    f.unauthenticated = True
+    return f
+
+
+def isunauthenticated(f):
+    """
+    Checks to see if the function is marked as not requiring authentication
+    with the @unauthenticated decorator. Returns True if decorator is
+    set to True, False otherwise.
+    """
+    return getattr(f, 'unauthenticated', False)