Add icons to preferences in download center

- Also added new playstore

Change-Id: I679746cf4ca1bfb8e9893c5ee877f2c3279c5fcf
Allow changing theme to Holo.Light without crashing
Themes that attempt to change the settings theme's parent to
Holo.Light will end up crashing wifi settings.

Themers should override Theme.Settings.Base and leave Theme.Settings.Holo
alone.  Attempting to theme Theme.Settings.Holo will result in crashes
when accessing wifi settings.

This was patch was adapted from
tung91/android_packages_apps_Settings@007f03b

Change-Id: I61951b892acac6304d2c3dd02999eb70af93eef9