fixed sphinx doc generator

- arguments, return values indentation means they get correctly interpreted by sphinx
- functions with no return values were displaying return as ()
- return values were getting the '(optional)' added in some cases.

Example:
http://www.blender.org/documentation/250PythonDoc/bpy.ops.object.html

release/scripts/modules/rna_info.py

@@ -201,7 +201,7 @@ class InfoPropertyRNA:
             return "%s=%s" % (self.identifier, default)
         return self.identifier
 
-    def get_type_description(self, as_arg=False, class_fmt="%s"):
+    def get_type_description(self, as_ret=False, as_arg=False, class_fmt="%s"):
         type_str = ""
         if self.fixed_type is None:
             type_str += self.type
@@ -223,7 +223,9 @@ class InfoPropertyRNA:
 
             type_str += collection_str + (class_fmt % self.fixed_type.identifier)
 
-        if as_arg:
+        if as_ret:
+            pass
+        elif as_arg:
             if not self.is_required:
                 type_str += ", (optional)"
         else: # readonly is only useful for selfs, not args