add Package Index and Class Index files to each library's root path
(instead of at the reference/ root location), and add links to
these files in the left nav.

stage:
http://smain.mtv.corp.google.com:8080/reference/android/support/constraint/classes.html

Note: This depends on some style changes to enable highlighting these
new pages in the left nav: https://critique.corp.google.com/#review/147165269

TODO: Cleanupa all these 'wearableSupportPath' style hard-coded paths
and instead pass those paths as a doclava argument.

Change-Id: I13b4b441b46055551d36f0729de9b91ec98a0496
4 files changed