camera: Add a hwlevel attribute, annotate each metadata's hardware level

* Set each metadata key to one of full,legacy,limited.
* All keys present on the lower level must also be present on higher
  levels (i.e. all legacy keys present on limited/full devices, all limited
  keys present on full devices.)
* If a key is not annotated, it is assumed to be optional even on full.
  This is usually the case only for future, deprecated, or system keys.

Bug: 17788234
Change-Id: Ie88f3750cc06d889c6750f2099598d53ccb601b7
diff --git a/camera/docs/metadata_parser_xml.py b/camera/docs/metadata_parser_xml.py
index fb83490..b72c683 100755
--- a/camera/docs/metadata_parser_xml.py
+++ b/camera/docs/metadata_parser_xml.py
@@ -180,6 +180,11 @@
     d['synthetic'] = entry.get('synthetic') == 'true'
 
     #
+    # Hardware Level (one of limited, legacy, full)
+    #
+    d['hwlevel'] = entry.get('hwlevel')
+
+    #
     # Deprecated ?
     #
     d['deprecated'] = entry.get('deprecated') == 'true'