iColors: major update

* Use json prefs instead of sharedprefs
* Added custom nav button colors
* Automatic change the statusbar and buttons color based on the statusbar/navbar color if no custom colors are configure (I.E statusbar white can't have white statusicons no?)
* Some fixes all around

Change-Id: I8fccfc075069bc743dfc7334852cd1f3b0185893
Avoid JSON parse exceptions

Change-Id: I4e4cfb909ef47c24b2b5ae149df29288497e53a2