cli: when streaming to raw, respect the --prezeroed flag

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
streaming: add write counters to the Channels, implement more endpoints

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
sparse_dd: CLI requires local file destinations be specified with a file:// URI

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
vhd: ignore BAT table entries corresponding to blocks outside the current file size

Some vhd tools will create extra-large BATs in order to make future
resizes possible.

Signed-off-by: David Scott <dave.scott@eu.citrix.com>