PHP Strict Warning messages observed in SMS Provider configuration and Send SMS action

While working with CiviSMS, I observed a few different PHP strict warning messages.

1) Function signature mismatch on the inbound function

2) Error thrown when passing the array_keys($form->_contactDetails) into sendSMS

3) Unable to cast from array to string in $smsNotSent = array_diff_assoc call

I committed my changes to a private branch on GitHub: https://github.com/mmikitka/civicrm-core/tree/fix_twilio_sms_php_warnings