Added Find All Functionality to Ctrl-F searchbox.

Added a find all feature which works similarly to Sublime Text's find all. In the [Ctrl-F] searchbox there is an additional button which says "All". Hitting this button or pressing [Alt+Enter] will multiselect all results. It also closes the searchbox, so the user can immediately edit all the results.

The only changes in this commit are to searchbox.css and searchbox.js. 

How the new searchbox looks, with the addition of the "All" button.
![screenshot 2014-09-17 at 1 54 17 pm](https://cloud.githubusercontent.com/assets/6777709/4308531/ab8d864c-3e93-11e4-8dcb-5c7eba39bfbe.png)

After hitting Alt-Enter or the "All" button, the results are highlighted and the searchbox closes.
![screenshot 2014-09-17 at 1 55 55 pm](https://cloud.githubusercontent.com/assets/6777709/4308554/e51bf40c-3e93-11e4-8bf4-920850c82d7e.png)