Updated to androidx and android 28

[Burtan]

To use this library without jetifier with androidx, the support libraries have to be updated.

[franga2000]

The preference part of this library still doesn't work when used from androidx PreferenceScreen.

I am trying to port that part too, but I haven't found a good way of doing that without re-structuring and rewriting a large part of the code.

If anyone happens to have some experience with porting that kind of stuff, some help would be appreciated