Update React / Spring / MySQL example (#99)

* Update README.md title from NodeJS to Spring

Signed-off-by: Friedrich Greiner <greinerfriedrich@gmail.com>

* Always restart spring backend service

Signed-off-by: Friedrich Greiner <greinerfriedrich@gmail.com>

* Also pass db-password secret to spring backend

Signed-off-by: Friedrich Greiner <greinerfriedrich@gmail.com>

* Add healthcheck to the mysql service

 - a start_period of 30s + 15s (interval * retries) should be long enough for mysql to initialize

Signed-off-by: Friedrich Greiner <greinerfriedrich@gmail.com>