dialer_cdr/tasks.py: comment out periodic task task_pending_callevent

init plivo_app

add plivo_cloud to INSTALLED_APPS

add PlivoSubAccount model

add plivo_subaccount field to UserProfile model

show plivo_subaccount or gateway in form to add Customer depending upon settings.NEWFIES_DIALER_ENGINE

change NEWFIES_DIALER_ENGINE to plivo

add plivo lib to django-requirements.txt

add plivo credentials to settings.py

add plivo_cloud/admin.py

add on_delete=models.SET_NULL to UserProfile.plivo_subaccount field

remove aleg_gateway field from CampaignForm when NEWFIES_DIALER_ENGINE = plivo

make aleg_gateway optional for Campaign

populate aleg_gateway field in CampaignForm only when NEWFIES_DIALER_ENGINE = esl

in the task init_callrequest populate gateway only for NEWFIES_DIALER_ENGINE = esl

add code for handling init_callrequest task using plivo

add url plivo_cloud/answerurl

placeholder view for answerurl