This CR adds the ability to specify policies in configtx.yaml.  It is
one half of two required for users to specify their own policies.  The
second half is in FAB-9255 (submitted together) which takes these
additional config file options and encodes them into channel config.

Change-Id: I7ba264a7554d4e3656bf13f2191bd871ba401e21
Signed-off-by: Jason Yellick <jyellick@us.ibm.com>