streamchain

Cherry picking change merged in master

Conceptual information on orderers and the
ordering service generally, and then a
discussion of implementations, focusing on
Raft.

Change-Id: I679594b542d1496f9ee7b566f70f73ba84734607
Signed-off-by: joe-alewine <Joe.Alewine@ibm.com>
Signed-off-by: David Enyeart <enyeart@us.ibm.com>
(cherry picked from commit bf40f9857928278d0c923bde969d02dc38f5ddf5)