Modernize file uploads

Summary:
Modernizes file uploads. In particular:

  - Adds a mobile menu, with an "Upload File" item.
  - Adds crumbs to the list view, detail view and upload view.
  - Adds "Upload File" action to crumbs.
  - Moves upload file to a separate page.
  - Removes the combined upload file + recent files page.
  - Makes upload file use a normal file control by default (works on mobile).
  - Home page, file list and file upload page are now global drop targets which accept files dropped anywhere on them. Dragging a file into the window shows a mask and an instructional message.
    - User education on this is a little weak but I think that's a big can of worms?
  - Fixes a bug where dropping multiple files into a Remarkup text area produced bad results (resolves T2190).

T879 is related, although it's specifically about Maniphest. I've declined to make global drop targets yet there because there are multiple drop targets on the page with different meanings. That UI needs updating in general.

@chad, do we have an "upload" icon (counterpart to "download")?

Test Plan: Uploaded files in Maniphest, Differential, Files, and from Home. Dragged and dropped multiple files into Differential. Used crumbs, mobile.

Reviewers: chad, btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2190

Differential Revision: https://secure.phabricator.com/D4200

src/applications/directory/controller/PhabricatorDirectoryMainController.php

@@ -76,6 +76,7 @@ final class PhabricatorDirectoryMainController
     );
 
     $nav->appendChild($content);
+    $nav->appendChild(new PhabricatorGlobalUploadTargetView());
 
     return $this->buildStandardPageResponse(
       $nav,
@@ -491,7 +492,7 @@ final class PhabricatorDirectoryMainController
 
     $nav_buttons[] = array(
       'Upload File',
-      '/file/',
+      '/file/upload/',
       'upload-file',
       'Share Files');
     $nav_buttons[] = array(