Update MLKit dependency + Restructure code

• Update MLKit dependency, it's no longer part of Firebase.
• Restructure and simply code. Unnecessary classes were removed, and FaceBoundsOverlay was simplified so that it renders any boxes it receives. The heavy-lifting (which includes correcting the face bounds, scaling, and mirroring them) was moved to FaceDetector.
• Improve face detection. The previous face bounds correction was not entirely correct, which was resulting in the face bounds not being rendered exactly around the face (there were often offsets).

Update library dependencies

Update:

• Android support libraries version 28.0.0
• Firebase core version 16.0.4
• Firebase ML Vision version 18.0.1

Null frame data support

Add support for null data in frames incoming from a camera source

First stable non-beta release

• Add support for camera facing changes (Back camera, front camera)
• Fix abnormalities with face bounds rendering

First stable release

v1.0-beta

Pass orientation handler the camera's width and height