Summary:
Some transactions (like editing configuration values, task descriptions, or Conpherence images) can't be simply explained and need an additional larger element to show them fully (like a text diff).
Support change details like this in ApplicationTransactions. Implements the element in Config, so you can see changes.
Test Plan: {F32974}
Reviewers: chad
Reviewed By: chad
CC: aran
Maniphest Tasks: T2213
Differential Revision: https://secure.phabricator.com/D4984
