Better font size control

Change-Id: Idde7c08f655b0a11382c8af5a9a3d395ce655718
Show a preview of the selected font size immediately

Modified the font size preference dialog to show the user the selected
font size immediately. Also split the size description and percentage on
their own lines to show a preview of two different font sizes. In
addition, removed the gigantic title bar from the dialog.

Change-Id: Ifc1e930f9420bde0bb6fd61b1a395c3d36b4fb0b