Add adopt/abandon description to heat manual
Add adopt/abandon description to heat manual

Added adopt command description to heat manual.
Added note that adopt/abandon are disabled by default.

Change-Id: I36d0b70fe32750b82cd5fe9cf0403866b8501ed9

rdo-management/python-heatclient,tcpcloud/python-heatclient,tcpcloud/python-heatclient,rdo-management/python-heatclient,ecerulm/python-heatclient,openstack/python-heatclient,ecerulm/python-heatclient