Conpherence - Make the files widget more useful and ajaxify some more stuff

Summary: files widget updates as new files are added. made basically all edits "ajax" except for when you change the conpherence image which just does a reload. I will fix this in a future diff but it was starting to spiral out of control a bit.

Test Plan: commented on a task with files and noted the updated file widget. updated header image via drag and drop and dialogue -- noted a full reload. cropped image and re-titled conpherence - ajax updated as expected.

Reviewers: epriestley, chad

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2530

Differential Revision: https://secure.phabricator.com/D5288