add NumberProgressBar, use it at the AttachPreferenceProgressFragment

modify the progressbar to use the accent color as default color

thanks to @daimajia for creating this awesome widget!

Change-Id: I1fbfce031cf78270a18727bcea98c55b46be7f50
entropy: do not move random number generator to system

this should fix issues on HTC etc devices, which have a read only
system partition

Change-Id: I581dade509ff85c586f6f1c272fb2c6d04bc1ef7