Documentation for ALTO

Documentation for ALTO

Patch Set 4: Colin Dixon moving this abandoned gerrit change to here:
             https://git.opendaylight.org/gerrit/#/c/21600/1/

             That itself appears to be a flattening of:
             https://git.opendaylight.org/gerrit/#/c/20475/2
             and
             https://git.opendaylight.org/gerrit/#/c/20762/3/
             with a few other small changes.
Patch set 5: Edited according to comments on patch set 4.
Patch set 6: Removed double-include of ALTO user guide.
Pathc set 7: Edited according to comments on patch set 6.

Change-Id: I8fb263faf35a4c0704774c8b1dc46d32f00ebc39
Signed-off-by: Kai GAO <gaok12@mails.tsinghua.edu.cn>