benchDNA removed and replaced by example_DNA
Root outputs for example_DNA removed
Add signals USR2 and INFO for showing simulation status.

Add two signals : USR2 and INFO. After reception of one of these signals, Gate prints on the terminal a one line text describing the current progress of the simulation including current run id and current event id.
SIGINFO is not available on Linux.
Linux: $ pkill -SIGUSR2 Gate
Mac OS: CTRL + T sends a SIGINFO signal to the current process.
Example:
Run ID : 1 / 2 ; Event ID : 2645 / 10000 ; 13.4811 / 240 s [5.61%]
Make mixed DNA physics compilable from Geant4 9.5 to 10+.