Add option for embedded (iframe) Gitiles views.

[GoogleCodeExporter]

It is useful for applications wishing to embed Gitiles data to have access to a 
trimmed-down form of Gitiles pages that omit specifically the Gitiles header 
and footer, focusing only on the requested content. This is useful for 
applications wishing to embed Gitiles data in (for example) an iframe.

The ability to render a embedded view should be independent of the content of 
that view. In other words, the parameter should not use the "pretty" parameter. 
Instead, a "view" parameter is proposed. The default "view" value is the 
current view. However, alternative views can be supplied. In this case, the 
iframe-embeddable view would use "?view=embed".

Original issue reported on code.google.com by [email protected] on 17 Sep 2014 at 11:23