Fixes #4058 : Handle properties (CR and change msg) in the webapp

The properties are now stored in the LDAP, if missing are fetched in the
config file, or use default values.
Merge pull request #342 from VinceMacBuche/ust_4057/implem_4058/config_in_webapp

Fixes #4058 : Handle properties (CR and change msg) in the webapp