Add memory usage notifications (OOM flow control)

While doing some research on the different monitoring beans given to us in the JVM an idea came to me. It could be interesting to add a notification layer to LS when the system is getting close to OOM, we could archive this not hard with the different memory thresholds notifications provided directly by the JVM. What do you think?

Ref: https://docs.oracle.com/javase/8/docs/api/java/lang/management/MemoryPoolMXBean.html