Add to and remove from groups on every login based on config.

+ There is a config switch to enable automatic updating of group membership
  information on every login.
+ If the switch is on, whenever a user logs in, the group membership in CA
  is updated based on the group membership in LDAP.
+ Fix inverted logic issue in `userHasGroupLDAP` method.
+ Improve documentation in both code and stock configuration file.
+ Rename some configuration keys for clarity and consistency.