Method ConnectToDatabase

Open and close the connection to the SQLite database

• Parameter
  • bool close
    • If false, open database connection
    • If true, close database connection
• returns
  • SQLiteCommand
    • SQLite command method

First, we check if the local database already exist.
If it doesn't, we create it. We then define conn to be a SQLite connection with the database file.
Then, we define cmd as a SQLite command type from conn.
We then check if we should open or close the connection.
If we have to open the connection, we use conn.Open() to establish a database connection and, then, return cmd.
If we have to close it, we use conn.Close() after defining cmd to null. We then return cmd (null).