Provide additional option to calculate actual object size

(May be it was discussed elsewhere and I missed it, in that case I'm sorry )
Currently there's HeapSize interface, marked as the one useful to measure caches, and some implementation thereof computing the sizes of different objects.

I was thinking to add something like https://code.google.com/p/memory-measurer/ and provide sort of default implementation of HeapSize which can measure the size of arbitrary objects in bytes. Would require a javaagent to be hooked up.

Thoughts?