Partial update of navigation bar stuff
swap out more images
more iOS 7-ification
Update navigation back button code, making backButton use a UIBarButtonItem with a clear image. Clean up leftover methods in UIImage+SFCongressAppStyle. See #352.
Rename backButton to more generic clearButton.
Update back button stuff in SFPeoplePickerNavigationController to match SFCongressNavigationController. Make sure accessibility label exists.
Remove UINavigationBarBlueFlatBack image. We have tintColor and translucent = NO now. SFAppDelegate sets navigationbar.translucent to NO since the appearance proxy (used in SFCongressAppStyle) doesn't support that.
Set some alignmentRectInsets on backButtonImage to make it position better in the navbar.
Update UIIconsHamburger.
Merge branch 'feature/ios7er' into develop, fixing a mistake or two.

* feature/ios7er:
  Update UIIconsHamburger.
  Set some alignmentRectInsets on backButtonImage to make it position better in the navbar.
  Remove UINavigationBarBlueFlatBack image. We have tintColor and translucent = NO now. SFAppDelegate sets navigationbar.translucent to NO since the appearance proxy (used in SFCongressAppStyle) doesn't support that.
  Update back button stuff in SFPeoplePickerNavigationController to match SFCongressNavigationController. Make sure accessibility label exists.
  Rename backButton to more generic clearButton.
  Update navigation back button code, making backButton use a UIBarButtonItem with a clear image. Clean up leftover methods in UIImage+SFCongressAppStyle. See #352.
  more iOS 7-ification
  swap out more images
  Partial update of navigation bar stuff