Added separation of flags according to ordering

Summary:
Refs T2841 - Exactly what it says on the tin

Turned some ordering around.

 - Color is `ASC` to be in line with the flag dialog
 - Object type is `DESC`, since `TASK` and `DREV` are sure more of
   interest than `CMIT`

NOTE: May not work properly without D5514, since only a few
object handle types implement `getTypeName()` properly. The fallback
return value is `null`, after which we group when sorting per object
type. Dis gun b gud!

.

NOTE: Technically does not de-pend on D5517, though you may get a merge conflict. Prefer this one if you for some reason happen to push this one before D5517

Test Plan:
{F38202}
{F38203}
{F38204}

Reviewers: epriestley, btrahan

CC: aran, Korvin

Maniphest Tasks: T2841

Differential Revision: https://secure.phabricator.com/D5518

Conflicts:

	src/applications/flag/controller/PhabricatorFlagListController.php