Add an explicit dependency on features. Makes it clearer what the deps are for people enabling ucberkeley_cas from admin/modules.
Address post install message CB02 https://jira.berkeley.edu/browse/OPENUCB-254?focusedCommentId=182344
Link user to README on github for instructions about setting up a Calnet-enabled admin. Require that the Overlay module be disabled when we install.
Merge branch 'openberkeley-105'