Add slidebar in SettingsFragment to control epsilon

[AlstonLin]

Right now, we just make epsilon calculated automatically at each training and compare it directly with that value.

We should add a SlideBar in the Settings where the user can control the multiple of epsilon that the prediction algorithm compared with (i.e. if predicted < epsilon, user is impostor) from 0.3 to 30x epsilon (slidebar should scale logarithmically). Default should be 1x

This allows the user to control the strictness of the lock screen to what they like.