Implement the VM interfaces for memory management

The memory management facilities are split over four beans, which divide the concept into general memory managers, garbage collectors and resource pools. The main issue will be working out how many memory manager/garbage collector beans to return, and how to interact with MMTK to get the required data.

Rather than returning simple values, these return new instances of classes which provide quite a lot of data about memory usage. The minimum implementation should not be too complex, but adding a lot of the optional timing mechanisms will take a while.