Attempts to create the specified file.

• Example: $package_ftp->create_file('myfile.txt');
• Sends the STOR command to the FTP server
• Checks for a valid connection and returns false if it isn't valid
• Tries to open a passive connection and returns false if that fails
• Attempts to establish a connection to the IP and port specified by the passive connection
• Sets a 'bad_file' error, tries to close the afore-mentioned connection and returns false if the response code isn't 150 (see check_response)