DB Connection

Hello Davoud, 
The new DBConnection class handles DB connections, it uses either MySQL or SQLite, SQLite is faster and require no prior setup

there is two important methods:
public void SQLite_insertFirms(List<Firm> firms, long experamentID,int day) 

this function takes the listof firmsand insert each firm's individual details into the database in each day.

public void SQLite_FirmStatistics(List<Firm> firms, long experamentID,int day, int num_firms)
this function takes the list of firms and record aggregate data into the database.