Gently deprecate the MEMORY variable

[itzg]

The variable name MEMORY is misleading since it really refers to the JVM heap allocation. While that amount of memory usage is the majority of the overall Java process memory usage it is not 100% of it. As such, it is too easy to interpret that the container memory resource limit should be set to the same value.

A new variable naming should be introduced such as JAVA_HEAP which will be the shortcut setting for MAX_JAVA_HEAP and INITIAL_JAVA_HEAP. All of the above should use the MEMORY equivalent when set.

When the MEMORY variables are explicitly set the startup scripts should output a deprecation warning and clarify that resource limit should be set higher.

The documentation should point out some recommendations or strategies for determining the additional non-heap amount to allow.