Add vdi extension to HDD files

Signed-off-by: Ippoippo <ippoippo-software@ippoippo-eco.com>
New attach device method

Basic code in place, but not tested manually.
Know this won't work yet, because need to create StorageController first.

Signed-off-by: Ippoippo <ippoippo-software@ippoippo-eco.com>
New Storage Controller class

Classes created and unit tested based on my understanding of how the API should work.

Issues with testing though.
Storage Controller creation seems to work and passes back a new StorageController ID.
Setting the type seems to fail though???

Next piece of work.

Signed-off-by: Ippoippo <ippoippo-software@ippoippo-eco.com>