docs(@angular/cli): updates to support a better wiki experience (angular#4899)

Author: Brocco

docs/documentation/_Sidebar.md

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+* [Angular CLI](home)
+* [Generate](generate)
+* [Stories](stories)

docs/documentation/overview.md renamed to docs/documentation/home.md

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+<!-- Links in /docs/documentation should NOT have `.md` at the end, because they end up in our wiki at release. -->
+
+# Stories describing how to do more with the CLI
+
+ - [Asset Configuration](stories/asset-configuration)
+ - [Autocompletion](stories/autocompletion)
+ - [CSS Preprocessors](stories/css-preprocessors)
+ - [Global Lib](stories/global-lib)
+ - [Global Scripts](stories/global-scripts)
+ - [Global Styles](stories/global-styles)
+ - [Angular Flex Layout](stories/include-angular-flex)
+ - [Angular Material](stories/include-angular-material)
+ - [AngularFire](stories/include-angularfire)
+ - [Bootstrap](stories/include-bootstrap)
+ - [Font Awesome](stories/include-font-awesome)
+ - [Moving Into the CLI](stories/moving-into-the-cli)
+ - [Movine Out of the CLI](stories/moving-out-of-the-cli)
+ - [Proxy](stories/proxy)
+ - [Routing](stories/routing)
+ - [3rd Party Lib](stories/third-party-lib)
+ - [Corporate Proxy](stories/using-corporate-proxy)