Encryption: Add a way to retrieve the encryption settings without providing the password. Returns only the used cipher and the password ID

Storage/VD: Add API to prepare a chain of images for use with filters

Storage/VD: Allow different filter chains for reads and writes (required by disk image encryption to encrypt images afterwards)

Main: missing MediumVariant.

Storage/VD + Main/ExtPackManager+VirtualBox+SystemProperties: handle unloading of VD plugin from VBoxSVC when extpack is uninstalled, fixes extpack uninstall problems related to VDPluginCrypt.dll on Windows

VD: Add API to query information about a filter

Storage/VD: Add methods to load a plugin from a given path/file. Preparation for support of VD plugins in extension packs

Storage: Add support for filter plugins

include/VBox/vd.h: de-C++ify the use of PARTITIONING_TYPE, and at the same time replacing it with a better matching type name which is less 'global'

Storage/VD: Add support for different sector sizes (only opening and reading and writing images, not creating them with a sector size other than 512 bytes)

Added VDIfCreateVfsStream for OVA importing/exporting - completely untested.

Storage/VD: stop sabotaging the resize of diff images

Storage: Introduce new flag to skip unnecessary consistency checks in the VMDK backend while opening an image in readonly mode to speed up opening snapshots

added new enum PARTITIONING_TYPE - Auxiliary data structure for difference between GPT and MBR disks. Structure VBOXHDDRAW was modified.

Storage: New return status code when a free block is read

Storage: Add VFS file glue for the VD library

Storage/VD: errors during closing all images in VDDestroy shouldn't be lost

VD: Add option to ignore flush requests

VD: API to repair corrupted images

Storage: Add async discard API

VD: Initial support to discard unused blocks in an image + support for VDI images

VD: Interface cleanup. Merge the two involved structures (generic interface descriptor and callback table) into one, remove the duplicated interface wrappers in the backends and move the interface definitions into separate headers separating public and private interfaces.

VD: New VDCopyEx() API which can speedup cloning of diff images when cloning a VM

Storage: Small cleanup. Drops VDImageIsAsyncIOSupported, it is completely unused and the best behavior is to fail in VDOpen like we do for all the other flags

include/: a/an nits

VD: Use S/G buffers instead of S/G arrays for VDAsyncWrite and VDAsyncRead (Preparation for moving the I/O cache in front of VD, see #5295)

VD: Move the generic virtual disk framework + backends to src/VBox/Storage and rename the files to get rid of the HDD part because it supports floppy and DVD images too