Add queueSizeLimit setter on Liquid sharedInstance

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
Increment queued failed requests by 2, instead of 1

* Unauthorized request retries are still incremented by 1 (retried in intervals of 15 seconds)
* Rejected request retries are incremented by 2 (retried in intervals of 1 hour)
* Max number of tries is 40

This will reduce the number of failed retries by an half.

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
Add a minimum value for queue flush interval

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
Merge branch 'queue_optimizations' into development