Show channel status description

[pmallol]

Version dev-3d17906 (build 578)

Channels that don't report status update, such as Africa's Talking channels, remain in a grey and undefined status.

Considering the user still has to refresh the page to see any status update (#401), it would be helpful if there was a hint for the channel that is working properly, even though it's status color won't change.

[matiasgarciaisaia]

The Channel Service is trying to check the channel status (as reported by Africa's Talking) by using a Twilio API.

[matiasgarciaisaia]

Also, the Verboice code that should be abstracting Africa's Talking API has (probably dead) code that's copied from the Twilio implementation.