Refactored BrowserHelper's getInstalledSupportedBrowserNames
Refactored opt-out to use log:event:override:

Also changed "Metrics tracking" to "Usage Reports" and added "Send usage reports to Wikimedia to help us improve the app".
Abstracted logging and browser prefs to CommonsApp

Keeps NSUserDefaults stuff less dispersed.
Removed redundant "Safari" fallback checks

No longer needed because in "application:didFinishLaunchingWithOptions:" the call to "[[NSUserDefaults standardUserDefaults] registerDefaults:" ensures the value will be "Safari" by default.
Fixed alpha sort issue with browser list

Had been swapping the selected browser with the first browser in the list to cause the selection to appear on top, but this caused the items below the first one to no longer be alpha sorted. No more swapping - the selection is now removed and re-added to the front of the array thus leaving alpha sort of remaining browsers correct.