Catch unhandled exceptions in index.php

Summary:
When there is an exception in `index.php` then we currently get only blank screen.
Print it instead.

Test Plan: Thrown exceptions on several places of `index.php` and controller, got best results.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D3619

webroot/index.php

@@ -109,10 +109,6 @@ try {
 
   PhutilErrorHandler::initialize();
 
-} catch (Exception $ex) {
-  phabricator_fatal("[Initialization Exception] ".$ex->getMessage());
-}
-
   PhutilErrorHandler::setErrorListener(
     array('DarkConsoleErrorLogPluginAPI', 'handleErrors'));
 
@@ -259,6 +255,11 @@ if (DarkConsoleXHProfPluginAPI::isProfilerRequested()) {
     $profile_sample->save();
   }
 
+} catch (Exception $ex) {
+  phabricator_fatal("[Exception] ".$ex->getMessage());
+}
+
+
 /**
  * @group aphront
  */
@@ -352,11 +353,15 @@ function phabricator_fatal($msg) {
 
   global $access_log;
   if ($access_log) {
+    try {
       $access_log->setData(
         array(
           'c' => 500,
         ));
       $access_log->write();
+    } catch (Exception $ex) {
+      $msg .= "\nMoreover unable to write to access log.";
+    }
   }
 
   header(