This adds a description of the qcow2 file format to the docs/ directory.
Besides documenting what's there, which is never wrong, the document should
provide a good basis for the discussion of format extensions (called "qcow3"
in previous discussions)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
