Customizable second column for card browser (Issue 1310)

I've made the second column of the card browser semi-customizable, as per [Issue 1310](https://code.google.com/p/ankidroid/issues/detail?id=1310). By default, it shows the answer side of the cards in the second column instead of the deck name, and users can change the column via a spinner.

Rendering of the question/answer is very slow, so I do it in the background after the initial search is complete, and periodically fill in the missing values so that performance isn't affected. The rendering is aborted whenever another background task is initiated, as well as when the user closes the browser activity.

Finally, the add card from saved data (i.e. dictionary add from intent) was using the same template as the browser for showing the saved data, which is dangerous because changing the layout can have unintended consequences. So I also separated these layouts and optimized them for their respective tasks.

![untitled](https://cloud.githubusercontent.com/assets/2818274/2566924/d055c88c-b8cd-11e3-834c-09f3c0c75781.png)

I have prepared a binary which people can test out here before the code is merged in the main branch:
https://github.com/timrae/Anki-Android/releases/tag/v2.2browserAlpha4