docs(api/dart): avoid duplicate entries and fix breadcrumbs

[chalin]

Currently two entries are generated for top-level library members like classes, and the main API page for these members has no-so-useful breadcrumbs. E.g., the main API page for PipeMetadata has breadcrumb: angular2 > angular2 > PipeMetadata, vs. the proper breadcrumb angular2 > angular2.core > PipeMetadata that appears on the second copy of the API page entry.

TLDR; within the angular2 package there is a top-level catch-all library of the same name the exports most of the contained libraries. This results in duplicate API page entries (one for angular2.foo and one for angular2.some_sub_lib_id.foo). Furthermore, all internal page links to foo go to angualr2.foo so we loose breadcrumb information. This commit fixes the issue by hiding the top-level angular2 library definition only for the purpose of running dartdoc.

[chalin]

@kwalrath @wardbell @Foxandxss : ready for review.

I also did a minor cleanup, removing superfluous parentheses in the language regex.

[chalin]

Travis doc build is green. The failure is due to the e2e toh-6 flake.

[kwalrath]

The doc builds, but I don't see a difference in the output, compared to what's on angular.io. What should I look at/for?

[chalin]

Visit, say, Pipes, and then follow the PipeMetadata link in the Inheritance section. On ng.io it will bring up a page in dartdoc format. With this fix, it is in ng.io format.

[kwalrath]

Ah, OK. So those files are still being generated, but they aren't being linked to. Good. (Or at least better, if still not perfect.)

E.g., locally, I can still see http://localhost:8080/docs/dart/latest/api/angular2/PipeMetadata-class.html, but I guess it isn't linked to?

[chalin]

Yes.

Anything else to do before this is merged?

[kwalrath]

@wardbell or @Foxandxss does the code look good to you?