cmstats: Remove preferences and always enable stats

 * Not having an accurate count of how many people are using CM is
   painful. I am making an executive decision to remove the opt-out and
   always turn stats on. The data is anonymized and there is nothing
   evil that can be done with it. The only purpose here is to tell us if
   we are a successful project or not.

Change-Id: I915c5e824d4e15c05feb37a3d8ed911464b5d61b