Upgrade tools from 2.3.3 to 3.1.2
Upgrade build-tools from 26.0.2 to 27.0.3
Upgrade com.google.gms:google-services from 3.0.0 to 3.2.0
Downgrade kotlin version from 1.2.40 to 1.2.30 to match Android Studio Kotlin plugin version
Add google() repository
Set org.gradle.configureondemand to false (must also be disabled in AndroidStudio preferences
Fix issues related to these upgrade (compile -> implementation, etc.)

Convert RiotAppCompatActivity from Java to Kotlin and add Javadoc and log in onResume()
Rename stopWaitingView() to hideWaitingView()
Bugfix: ensure waiting view is hidden in case of error