ts2dart should transpile angular2 doc comments to dartdoc comment format

[naomiblack]

See http://www.dartdocs.org/documentation/dartdoc/0.6.2/index.html#dartdoc

This includes:

• making sure that none of the js-specific API ends up in dartdoc
• making sure that the js-specific comment annotations (e.g. @public) don't show up in the docs
• making sure that links are correctly formed
• making sure that only the public API surface is listed in the published doc output (via a manifest or some kind of filter?)
• making sure that examples are Dart version, not TypeScript, via either ts2dart on a source TS example, or via an author-override