replace obsolete logic for meta tags with include provided by devsite,
and add data attributes to the ReferenceObject itemprop tag that carry
api level information for the future version of the API level selector.
Note that if the build specifies 'library.root' then that is still used
to specify the _book.yaml location in a django variable. This way,
we still have control from the DevSite include as to whether we use it.

TODO: Add these data attributes to the rest of the template for
method/member docs. (I don't want this CL to be too messy.)
bug: 67899891
bug: 69369545

Test on both support library and framework doc builds.
Example from framework build:
<head>
  <title>ProgressDialog</title>
  {% include "_shared/_reference-head-tags.html" %}
  <meta name="body_class" value="api apilevel-1" />
</head>
<body ...>
<div itemscope itemtype="http://developers.google.com/ReferenceObject"
     data-version-added="1" data-version-deprecated="26" >
<!-- This DIV closes at the end of the BODY -->
  <meta itemprop="name" content="android.app.ProgressDialog" />
  <meta itemprop="path" content="Deprecated" />

Example from support lib build:
<head>
  <title>DynamicAnimation</title>
  {% setvar book_path %}/reference/android/support/_book.yaml{% endsetvar %}
  {% include "_shared/_reference-head-tags.html" %}
  <meta name="body_class" value="api apilevel-26.1.0" />
</head>
<body ...>
<div itemscope itemtype="http://developers.google.com/ReferenceObject"
     data-version-added="26.1.0" >
<!-- This DIV closes at the end of the BODY -->
  <meta itemprop="name" content="android.support.animation.DynamicAnimation" />
  <meta itemprop="path" content="Support Library" />

Change-Id: Ibda945b90fe74f594637d93b987a596ff5cf36bd
4 files changed