simplify QueueStatisticsManager unit tests
remove unused code
rename ami_wrapper to _ami_class
add comment on unused class

Need to do something about it, i.e. either use it or remove it.
remove unused logger
simplify tests in TestQueueDao

Remove useless tests. Make tests more similar.
refactor QueueDAO to use QueuesList reverse index
simplify idbyqueuename implementation
use QueueDAO instead of QueueServiceManager

Remove completely QueueServiceManager. This was doing the same job as
QueueDAO.
remove queue related methods in InnerdataDAO

Use those in QueueDAO instead.
use xivo_cti.dao instead of xivo_dao in QueueStatisticsManager

So that we don't do a database requests each time the get_queue_summary
method is called.
move some logic from QueuesList to QueueDAO
move more logic from QueuesList to QueueDAO
add test on queues_by_name
remove unused imports
add get_id_as_str_from_name method to QueueDAO

Used for compatibility purpose.
use exists in place where is_a_queue is used
remove unused CachingQueueStatisticsManagerDecorator class

Might be useful on large installation, but is currently (and has been
since a while) not used, so removed it altogether. We would need to take
some measure before addding it back.
assert_never_called was checking nothing

Replace occurences with self.assertFalse(mock.called)
Merge remote-tracking branch 'origin/queue-stats-mgr-unused-caching'