android-sdk: strip down to basic sdk

As this image is now to be used as a persistent container, it is now up
to the users of it to install/upgrade their components to suit their needs
and to do so as and when new releases become available.

Signed-off-by: Paul Campbell <pcampbell@kemitix.net>
android-sdk: include note of apt packages installed

Signed-off-by: Paul Campbell <pcampbell@kemitix.net>
android-sdk: make sdk directory available as a volume

This allows the container to be persistent.

Signed-off-by: Paul Campbell <pcampbell@kemitix.net>
android-sdk: upgrade to 23.0.1

Signed-off-by: Paul Campbell <pcampbell@kemitix.net>
android-sdk: add note about usage

Signed-off-by: Paul Campbell <pcampbell@kemitix.net>
android-studio: start container with android-sdk volumes

Signed-off-by: Paul Campbell <pcampbell@kemitix.net>
android-studio: add tests for existence of persistent containers

Signed-off-by: Paul Campbell <pcampbell@kemitix.net>
Merge pull request #24 from kemitix/feature/android-sdk-as-persistent-container

Feature/android sdk as persistent container