Definition of a basic I/O interface (to/from files and/or Database).

The DataManager is intended to provide a unique interface to access Objy DB or ASCII files containing e.g. calibration data about EMCAL.

Basic usage :

 // The DataManager (DM in short) class is a Singleton.
 emcDataManager* dm = emcDataManager::GetInstance() ;
 // Ask the DM	to show its list of plugins (1 plugin=1 emcObjectManager)
 dm->ls() ;
 // Ask the DM to collect gains at a given time
 PHTimeStamp when(2000,6,20,12,30,00) ;
 emcGains pilot ;
 emcGains* collected ;
 pilot.SetSource(emcManageable::kDB_Objy) ;
 collected = dynamic_cast<emcGains*>(dm->Collect(pilot,when)) ;
 if (!collected) {
   // something went wrong...
 }