Updated CodeIgniter to 2.1.4

- Also applied changes to OpenVBX core files to fix compatibility
- See https://github.com/twilio/OpenVBX/issues/258
- Also see 4d899e193d53aedf9240db702946fdcee516b2f6 in master branch
Updated config file for newer CodeIgniter

- May cause issues for installations that are not being rewritten
- Installation-specific options should be saved in `-local.php` config files!
Fix mail_helper to use CodeIgniter email library

- Much better support for SMTP
Updated Twilio library to twilio-php/3.12.1