getHostLocation() added to IVirtualDisk and it's implementation.

The new method returns an URI which represents the location of the
virtual disk on the host system. Used URI as the format as this is the
most general one and can be used for nearly every thinkable scenario of
location of a virtual disk.
extended VDiskFile. Still work in progress.
CommandLineInterface class works now with a location (VDiskFile).

This allows to have a state that represents a location on the virtual
disk and includes automatically the loaded disk.
Constructor does not need IVirtualDisk parameter if the parent contains
it
fixed to early call to setHandled()
added change directory (cd) command to the CLI
Merge branch 'master' of https://github.com/groggi/eth-jcd
added command to create a directory (parent has to exist for now)