[NaCl Addin] Add new property for setting name of index page.

As a result of this change we no longer need to ship the
.user file for the hello_world_gles example, which is good.

Also, add missing index_pnacl.html.

BUG=

Review URL: https://codereview.chromium.org/11359218

git-svn-id: https://nativeclient-sdk.googlecode.com/svn/trunk/src@1467 050acbb0-2703-11df-ab0a-9f3f633ae91d
10 files changed