[KARAF-2434] Add a quick update on the manual about JAAS users, groups, and roles.
[KARAF-2434] Add a quick update on the manual about JAAS users, groups, and roles.

git-svn-id: 71d8a689455c5fbb0f077bc40adcfc391e14cb9d@1527599 13f79535-47bb-0310-9956-ffa450edef68

grgrzybek/karaf,grgrzybek/karaf,grgrzybek/karaf