Improvements in HTTP requests queue (LQQueue)

* Each rejected request retry is postponed for 1 hour.
* Each unauthorized request retry is postponed for 1 minute.
* Each unreachable request will be retried on next flush.

Signed-off-by: Miguel M. Almeida <miguelcma@CMA-Retina.local>
Fix on UIColor conversion to hex

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