class AliPHOSDigitizer: public AliDigitizer

*-- Author :  Dmitri Peressounko (SUBATECH & Kurchatov Institute)

 This class performs digitization of Summable digits (in the PHOS case it is just
 the sum of contributions from all primary particles into a given cell).
 In addition it performs mixing of summable digits from different events.
 The name of the class is also the title of the branch that will contain
 the created SDigits
 The title of the class is the name of the file that contains the hits from
 which the SDigits are created

 For each event two branches are created in TreeD:
   "PHOS" - list of digits
   "AliPHOSDigitizer" - AliPHOSDigitizer with all parameters used in digitization

 Note, that one can set a title for new digits branch, and repeat digitization with
 another set of parameters.

 Use case:
 root[0] AliPHOSDigitizer * d = new AliPHOSDigitizer() ;
 root[1] d->Digitize()
 Warning in <TDatabasePDG::TDatabasePDG>: object already instantiated
                       //Digitizes SDigitis in all events found in file galice.root

 root[2] AliPHOSDigitizer * d1 = new AliPHOSDigitizer("galice1.root") ;
                       // Will read sdigits from galice1.root
 root[3] d1->MixWith("galice2.root")
 Warning in <TDatabasePDG::TDatabasePDG>: object already instantiated
                       // Reads another set of sdigits from galice2.root
 root[3] d1->MixWith("galice3.root")
                       // Reads another set of sdigits from galice3.root
 root[4] d->Digitize("deb timing")
                       // Reads SDigits from files galice1.root, galice2.root ....
                       // mixes them and stores produced Digits in file galice1.root
                       // deb - prints number of produced digits
                       // deb all - prints list of produced digits
                       // timing  - prints time used for digitization