Merge branch '206-settings-prefs-alt' into 'master'

Material design settings - alternative

Closes #206.

Alternative to !77 that does not rely on an additional external library. The two alternatives should be compared for backwards-compatibility specifically regarding the ringtone selector.

Includes code from https://github.com/consp1racy/android-support-preference
License: Apache License v2.0

See merge request !78