Cleanup for Laravel 5.2 upgrade

Summary:
Some tasks remained to do for a better Laravel 5.2 app/ folder style:

• remove app/Listeners/ subfolders
• ensure classes and files' names match

This is a follow-up for 0e1390e5. Rel. T840.

Test Plan: no op

Reviewers: dereckson

Maniphest Tasks: T840

Differential Revision: http://devcentral.nasqueron.org/D444