The navigation.json is now passed through the dgeni pipeline.
The source file has been moved to `aio/content/navigation.json`
but the generated file will now appear where the original source file
was found, `aio/src/content/navigation.json`.
Everything inside `aio/src/content` is now generated and ignored by git.
The `processNavigationMap` processor in this commit adds the current version
information to the navigation.json file and verifies the relative urls in
the file map to real documents.
The navigationService exposes the versionInfo as an observable, which the
AppComponent renders at the top of the sidenav.
Implemented style guide elements to top header bar, side hamburger nav menu, content and search. Consolidated SCSS files to styles folder. Fixed PWA test.
All the docs related files (docs-app, doc-gen, content, etc)
are now to be found inside the `/aio` folder.
The related gulp tasks have been moved from the top level
gulp file to a new one inside the `/aio` folder.
The structure of the `/aio` folder now looks like:
```
/aio/
build/ # gulp tasks
content/ #MARKDOWN FILES for devguides, cheatsheet, etc
devguides/
cheatsheets/
transforms/ #dgeni packages, templates, etc
src/
app/
assets/
content/ #HTML + JSON build artifacts produced by dgeni from /aio/content.
#This dir is .gitignored-ed
e2e/ #protractor tests for the doc viewer app
node_modules/ #dependencies for both the doc viewer builds and the dgeni stuff
#This dir is .gitignored-ed
gulpfile.js #Tasks for generating docs and building & deploying the doc viewer
```
Closes#14361
