[core-api] New Feature: Store information about the installed modules

  * Upon initialization, information about the installed modules is kept
    in an instance of InstallationData
  * In the future, this information will be usable to perform automatic
    store upgrades
New Feature: Added public API to verify if a DomainObject is valid
[jvstm-ojb] Deleting a OneBoxDomainObject will put a DELETED_VALUE in the VBox