Thanks to the previously merged DS-1180, the LDAPHierarchicalAuthentication
method gaind the capabilities of LDAPAuthentication. This commit renames
LDAPHierarchicalAuthentication to LDAPAuthentication and removes the
Hierarchical LDAP originally assumed that when search.user is not
set, anonymous search is performed. We now assume that if it's
not set, simple LDAP authentication is performed. That retains
configuration backward comaptibility for the two most common cases.
The special case of anonymous search now requires search.anonymous
to be set to true, which means old installations using this setup
will have to add this config property.