master: start to document ecallmgr maintenance routines
carrier_ordering: access the validation errors json object
carrier_ordering: update to only support put/post
3.16: correct misspelled module name
3.16: check 'conflict' error on media upload

sometimes when uploading attachments, 'conflict' errors occur, but the
upload was actually successful. Check the doc's _attachments for the
existence of the attachment before retrying the upload
Merge pull request #504 from 2600hz/carrier_ordering

Carrier ordering
KAZOO-2910: Fix weight_cost and return summary view for colleciton update
KAZOO-2910: Adding enabled classifiers to the view
KAZOO-2910: Add all classifiers to view
Added support for preflow ringback that calls a module to get dynamic
ringback. For perfomance, it also allows passing an opaque from this module
to preflow