[Clas12_software] OSG generators update

[Maurizio Ungaro]

Dear all:

The clas12-mcgen version on the OSG Clas12 Simulation Portal has been updated to v2.13.

Updates:

## MCEGENpiN_radcorr:
 
- fixes output file generation

## dvcsgen

- force t to be in the range of tmin < t < tmax
- add global fitting of the form factors
- save phi angle in the Trento Convention instead of BMK


Regards,

Nathan & Mauri