(IcingaWeb2) Move configuration (user preferences) backend from INI
files to a dedicated pgSQL db.

(IcingaWeb2) LDAP:

- procedure to automatically issue service credetinals to authenticate
  with the ldap server.

- starttls secured ldap connection with service account.

- use of the variable `base_dn` instead of hard-coded values in config
  files.

(IcingaWeb2) CONFIGURATION:

- fixed rsync parameters.

- resource renaming.