Squashed commit of the following:

commit cfe928ec76df2794aaa8ac96abd2f63bb4feec63
Author: Walter C <wachen@mozilla.com>
Date:   Thu Jun 13 14:54:46 2013 +0800

    Remove cost_control.turn_on_ftu()

commit eb8c5211a52b1e5541c09747e1f666c2d2816b55
Author: Walter C <wachen@mozilla.com>
Date:   Thu Jun 13 14:15:25 2013 +0800

    fixed PEP8 issue

commit efba7e44c3bd44eba306007189da68d37a0f21a0
Author: Walter C <wachen@mozilla.com>
Date:   Tue Jun 11 17:28:05 2013 +0800

    Fixed all ftu related stuffs, added some additional functions, fixed some bad logic.
Build on ypwalter's changes to the Cost Control FTU.