[Murano Docs] [CLI] Manage environments
[Murano Docs] [CLI] Manage environments

Adds the Manage environments sub-section to the Using CLI section
of the End User Guide.

Change-Id: I03e298c337c85dcddd7d7aa402bac4cb3718434b

NeCTAR-RC/murano,satish-avninetworks/murano,DavidPurcell/murano_temp,NeCTAR-RC/murano,DavidPurcell/murano_temp,olivierlemasle/murano,NeCTAR-RC/murano,olivierlemasle/murano,olivierlemasle/murano,satish-avninetworks/murano,olivierlemasle/murano,NeCTAR-RC/murano,openstack/murano,openstack/murano,satish-avninetworks/murano,satish-avninetworks/murano,DavidPurcell/murano_temp,DavidPurcell/murano_temp