remove unused "delayed_action" function in AMI class

By removing this function, more unused code can be removed.
remove unused functions in AMIClass class
remove unused "xivoremote" code

I believe it's mostly a remnant of XiVO 1.1 inter-xivo connections.
This code is most probably never executed, and even if it was, it was
doing nothing since there is no code to handle the the 'xivoremote'
action that it is queueing.
remove more unused code around self pipe trick implementation
remove unused code in notify_step of asyncActionsThread

While looking around at functions which called the cb_timer function, I
found some unused code, so I removed it.

The CTI client does nothing with the "faxsend" message when it contains
a "step" key.
remove unused schedule_answer method in CurrentCallManager
refactor how tasks are queued to the main thread

Before, if you weren't in the main thread and you wanted to execute
something in the main thread, you needed to call the cb_timer with a
specific dictionary and make sure that the checkqueue method took the
appropriate action when that dictionary was read in the main thread.

Now, you pass a function and its arguments (i.e. a task) to the
queue_task method, which queues it and the task will be eventually
executed in main thread.
extract task queue from the CTIServer class

Also, code using the scheduler are now executing their callback in the
main thread instead of a non-main thread. This was problematic for the
PeopleCTIAdapter/Dird class, where there was a race condition.
remove unused logger
update Dird tests

It isn't using a scheduler anymore.
rename queue module to task_queue
remove some unused code
rework Task interface
replace scheduler with task_scheduler
empty the cti events queue after running the task scheduler

Otherwise, if a scheduled task was calling send_cti_events, the event was
only read from the queue the next time the select loop returned, i.e.
two calls to select was needed before the event was actually sent to the
CTI client.
move self._update_safe_list out of for loop
use a deque instead of a Queue

These functions are not called anymore from the non-main thread.
Merge remote-tracking branch 'origin/blocking-operation'