Multi-result search view updates

* Adds ListResultsActivity to isolate action bar and backstack concerns.
* Re-uses ListResultsFragment inside ListResultsActivity rather than adding to BaseActivity.
* Simplifies options menu and backstack hackery in BaseActivity.
* Updates search result list view.
I'm definitely leaning more in that direction. I figured I would try it out here to see how it felt and to re-ignite the conversation.

I'd be up for making the switch but if we move wholesale to hipster annotations I would also want to move to 2-space indent to better fit things on a single 100-character line. This would make for a messy transition or a massive reformat.

But then the Square-ification of our code would be complete ;)