[Auth] use mustache for ldap auth handler

Signed-off-by: Ralf Grawunder <r.grawunder@googlemail.com>
[Auth] - baseAuthAdapter calls all methods despite errors (handling at in the end)
       - ldapAuthHandler uses new ldapClientHelper
       - shorter error messages
[Helper] - new ldapClientHelper to replace old ldapAuth

Signed-off-by: Ralf Grawunder <r.grawunder@googlemail.com>