Embedded specific instructions should be included for keeping the GC heap small

This is item #1 from JDK-8138571.

While working with a customer it was discovered that using the following options helped keep the java heap small, saving dynamic footprint for the customer:

-XX:MaxHeapFreeRatio=10 -XX:MinHeapFreeRatio=5

Note the defaults for these two options are 70% and 40%. There are likely some performance sacrifices being made with these small settings. Customers who care about small footprint should tune them down as much as possible without introducing more performance degradation than they find acceptable.

This also relates to JDK-8146436 "Add UseAggressiveHeapShrink option". Customers trying to keep the heap small should also add -XX:+UseAggressiveHeapShrink, presuming it is added to JDK 9 (as of now it is a feature request).

This CR is a request to make sure there is documentation in place to explain the above to embedded customers.