Icons should be replaced with icons from the android-21 SDK
The current icons are from the Holo theme, are transparent, have a subtle border around them, and don't fit in next to the "Up" and "Menu" buttons that the material design theme provides. Thus, we should replace relevant icons from the holo theme with those from the material theme.
We will need to ensure that copies for each of the different drawable-* folders are available, including ones we may not yet have a folder for, e.g. drawable-xxxxxxxxxxxhdpi - if they are there yet ;).