Added LicenceToBill::Error to wrap error statuses
Exposed data_source from LicenceToBill::Concerns to be able to access data referenced by UpCased keys.

For instance, errors now looks are now  LicenceToBill::Error with @data_source = { "Status" => 401, "Message" => "Bad key" }

And there is no way to access the Status/Message "objects" through method_missing method calls because Ruby don't allow method names to start with a capital letter