Use FrameLayout for root layout instead RelativeLayout

`FrameLayout` avoid double measuring that `RelativeLayout` do.
When UI appearing time is about ~40 ms, hard to see result of small optimizations. Based on logs It looks the same as was before. But the result of removing `RelativeLayout` can be visible inside profiler. Sections with measuring is much less without `RelativeLayout`. I'll add trace-file and screenshot to merge request.
UI appearing time (landscape orientation, video paused, animation disabled):
Samsung Note 4, Android 6.0.1 (release): ~58 ms.