Projects may want to handle check-pointing within their own application and skip the disk intensive requirements of a VM snapshot.

VBOX: When attempting to deregister the VM, if we are unable to acquire the session lock, exit the routine with an error. Avoid a crash.

VBOX: Configure a bunch of virtual functions to be purely abstract to avoid a bunch of compiler warnings in gcc

VBOX: Juha pointed out that I took one line of code out to many on a code cleanup pass.  I'm adding it back in.

VBOX: Fix crash if DVD-ROM media had been ejected by some external event.  Technically this shouldn't be happening, but something funky is going on with VirtualBox and we need to handle things that may cause a crash when cleaning up the VM.

VBOX: Make the service install scenario work again.

VBOX: When checking for the existence of a VM registered to a given slot directory, also check for the ISO Contextualization image and cache disk image.  If any type of media is registered to a given slot directory, close it regardless if it is attached to a VM or not.

VBOX: When deregistering a VM, organize the medium list by most recent child first and then release as needed.

VBOX: Introduce the notion of Virtualbox COM namespaces. We currently support VirtualBox 4.2 and VirtualBox 4.3.

VBOX: Do not attempt to restore the current snapshot if the VM hasn't been running long enough to generate one.

VBOX: If something fails during create_vm(), we must release the write lock before deregister_vm() is called. Handle machine and session cleanup at the end if the routine.

VBOX: Move common code to VBOX_BASE class, VBOX_VM derives from it by extending virtual functions calling Vboxmanage or Native API functions.  Use ATL on Windows to wrap COM Objects and data types.

VBOX: Begin refactoring for supporting the native VirtualBox API set on Windows.  Use the code in the deprecated directory as a baseline.