Rename LQQueueStatusFailed to LQQueueStatusUnreachable

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>
Improvements on error messages

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>
Sending data points with dates in UTC

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>
Do not try HTTP Requests if there is no Internet connection

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>