Add device attribute in Disk class

This attribute hosts the block device associated with this Disk
instance. This can be the the original media if the source media is a
block device, a loop device of the original media if the original media
is a regular file or a loop device of a temporary object if the original
media is a directory.
Add REG_{SZ,DWORD,BINARY} helper funcs in Registry

Those lambda functions are used to set a value of type REG_SZ,
REG_DWORD and REG_BINARY in a registry node
Extend SysprepParam class to include a value check

Extend the SysprepParam class to support defining a custom check
function which can be used to check if the value given by a user when
updating a sysprep parameter is valid.