send screen
Delete Provider model
Add Pingapp init class

* Pingapp class sets application defaults e.g. sms provider to use

* Add 'sender_number' config options in the SMS configuration file

* Register a route for SMS callback urls - Used by service providers to route
incoming messages to PingApp
Implement Model_Person::get_contact

* A contact and contact type are unique to a person
Merge remote-tracking branch 'origin/send_screen' into sms-message-dev

Conflicts:
	application/views/pages/dashboard.php
Send pings via SMS provider

* TODO: Catch and displays errors that occur while sending messages
Add migration for schema changes