We need compileSdk 28 and the required AGP and gradle versions, as well
as updating to compatible support library revisions.
minSdk and targetSdk needs to move to build.gradle from manifest.
buildToolsVersion isn't used anymore.
Also remove the 2.11 restriction on the root build.gradle file. It's
unnecessary, as the Android plugin will already error if the version is
too old. This means that the build will work on any version that is new
enough, which should be 2.10-2.12 at the time of writing.
