It's now possible to create a new file with specific size.

This should make importing big files a bit faster as the virtual disk
dies not have to create all the time new free spaces and therefore
extend the disk again and again.
implemented first import method into new class HostBridge.

The new class HostBridge provides the developer with as easy to use
as possible static methods. Those methods provide functionality used
to get some interaction going between the host's filesystem and the
virtual disk.
Fixed comments in VDiskFileOutputStream and added new constructor.

The new constructor uses the VDiskFile class to represent a file.
ImportCommand uses HostBridge now for the import