Move "Rendering References" to the DifferentialChangesetParser level

Summary:
Separates changeset IDs from rendering. Now each changeset has a "rendering
reference" which is basically a description of what the ajax endpoint should
render. For Differential, it's in the form "id/vs". For Diffusion,
"branch/path;commit".

I believe this fixes pretty much all of the bugs related to "show more" breaking
in various obscure ways, although I never got a great repro for T153.

Test Plan:
Clicked "show more" in diffusion change and commit views and differential diff,
diff-of-diff, standalone-diff, standalone-diff-of-diff views. Verified refs and
'whitespace' were always sent correctly.

Made inline comments on diffs and diffs-of-diffs. Used "Reply".

Reviewed By: tuomaspelkonen
Reviewers: tuomaspelkonen, jungejason, aran
CC: aran, tuomaspelkonen, epriestley
Differential Revision: 274

src/applications/diffusion/controller/change/DiffusionChangeController.php

@@ -32,9 +32,18 @@ class DiffusionChangeController extends DiffusionController {
     }
 
     $changeset_view = new DifferentialChangesetListView();
-    $changeset_view->setChangesets(array($changeset));
+    $changeset_view->setChangesets(
+      array(
+        0 => $changeset,
+      ));
+    $changeset_view->setRenderingReferences(
+      array(
+        0 => $diff_query->getRenderingReference(),
+      ));
     $changeset_view->setRenderURI(
       '/diffusion/'.$drequest->getRepository()->getCallsign().'/diff/');
+    $changeset_view->setWhitespace(
+      DifferentialChangesetParser::WHITESPACE_SHOW_ALL);
 
     $content[] = $this->buildCrumbs(
       array(