[ZD#696706] refactor code and show alert for private content

There isn't a good way to limit search results to only end-user content, they don't support section sideloads for the hc search endpoint. Instead we can sideload the section when getting the hc article content and add a 'private content' alert to the modal preview.

#### Changelog:

- add alert to modal when previewing private or internal content
- refactored to improve performance and prepare for Web Portal retirement
- use local storage to avoid a redundant query for the Web Portal topic content
- fixes UI bug where search submit button is dropping below input bar
- limit query results (we were getting back 100 results from the api/v2/search endpoint)

![answer-suggestion-wp](https://cloud.githubusercontent.com/assets/1010128/2933850/d12f71de-d7c4-11e3-8c72-53d58ad57026.gif)

#### References:

- [[ZD#696706] Answer Suggestion App gets results for restricted articles even when it is set to exclude them](https://support.zendesk.com/agent/#/tickets/696706)

/cc @maximeprades @princemaple @jdmanuel