camera_metadata: Add visibility support, and a HAL2 tag

- Add a visibility property which controls whether a tag is available
  only to the system, hidden in managed code, or public in managed code.
- Add a HAL2 tag to indicate HAL2.x-only tags
- Fix output/inputStream tags to be arrays.

Change-Id: I856d0b1bf413eefd58914e5b85b08331a4bf4536
diff --git a/camera/docs/metadata_parser_xml.py b/camera/docs/metadata_parser_xml.py
index 7b55273..4e5c35f 100755
--- a/camera/docs/metadata_parser_xml.py
+++ b/camera/docs/metadata_parser_xml.py
@@ -144,6 +144,11 @@
     d = {}
 
     #
+    # Visibility
+    #
+    d['visibility'] = entry.get('visibility')
+
+    #
     # Enum
     #
     if entry.get('enum', 'false') == 'true':