Add documentation on how to setup dev environment for Android development (to run tests)

The `functionalTest` suite has a number of Android specs that assume a dev environment suitable for them to run in. For any current or former Android developer, this is trivial, as they would have installed all the necessary tools since time immemorial. For non-Android JVM developers, this means they cannot run the full test suite. They can run all the JVM tests with `./gradlew funcTest --tests com.autonomousapps.jvm.*`, but the Android tests remain a bridge too far.

The Wiki and/or the readme should be updated with instructions on how to use the command-line `sdkmanager` to install the necessary tools from a clean slate.

This would be a good first issue for any Android developer who would like to help out :)

Start with the repository Wiki and/or README, then review the Android specs in the functionalTest suite and the JVM-only command ./gradlew funcTest --tests com.autonomousapps.jvm.*. Document how to use the command-line sdkmanager from a clean slate, including the tools needed to run the Android tests; done means a non-Android JVM developer can follow the instructions and run the full test suite.

Written by the indexing model from the issue text.