Add Dropbox Security Review.  Fixed rebase conflicts from last attempted rebase

Test Plan: .

Reviewers:

Differential Revision: http://local.dev:8000/D45

Conflicts:
	src/applications/herald/adapter/HeraldDifferentialRevisionAdapter.php
	src/applications/herald/config/HeraldActionConfig.php
	src/applications/herald/config/HeraldValueTypeConfig.php
added ACTION_MARK_SECURITY in a few more places
Merge branch 'herald-security-fixed-rebase'