Move FontIcon calls to Icon

Summary: Normalizes all `setFontIcon` calls to `setIcon`.

Test Plan: UIExamples, Almanac, Apps list, etc.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, hach-que, yelirekim

Differential Revision: https://secure.phabricator.com/D15129

src/applications/diffusion/application/PhabricatorDiffusionApplication.php

@@ -14,7 +14,7 @@ final class PhabricatorDiffusionApplication extends PhabricatorApplication {
     return '/diffusion/';
   }
 
-  public function getFontIcon() {
+  public function getIcon() {
     return 'fa-code';
   }