Have xenstored initialise its connections, meaning that xend can be out of

Have xenstored initialise its connections, meaning that xend can be out of
that loop completely -- the xc_init_store, initDomainStore calls can all go.

Have xenstored understand where the local domain information goes.  Xend no
longer has to generate a path and pass it to xenstored through
xs_introduce_domain -- we just allow xenstored to generate the path, and then
call GetDomainPath later.  There is still some work required to tidy this up.

Change the uuid module to generate uuids as lists of bytes, not in the
stringified form.  Added a unit test for that module.

Change the semantics of Xend restart, relying on these changes to the
xenstored semantics and earlier changes to add an opaque handle to the
hypervisor's domain-specific data block.  The semantics are now clearer, as
Xend can validate whether the details in the store match the current live
domain.

Added a usage statement to xenstored.

Some of this code is by Steven Hand.

Signed-off-by: Ewan Mellor <ewan@xensource.com>